\(A=\dfrac{1}{2+\sqrt{3}}+\sqrt{4-2\sqrt{3}}\)

\(=\dfrac{2-\sqrt{3}}{2^2-\left(\sqrt{3}\right)^2}+\sqrt{\left(\sqrt{3}-1\right)^2}\)

\(=2-\sqrt{3}+\left|\sqrt{3}-1\right|\)

\(=2-\sqrt{3}+\sqrt{3}-1\)

\(=1\)

( Vì \(3>1\Rightarrow\sqrt{3}>1\Rightarrow\sqrt{3}-1>0\))

Vậy A = 1

Read the following passage on transport, and mark the letter A, B, C, or D on your answer sheet to

indicate the correct answer to each of the questions from 43 to 50.

(1) In the West, cartoons are used chiefly to make people laugh. The important feature of all these cartoons is the joke and the element of surprise which is contained. Even though it is very funny, a good cartoon is always based on close observation of a particular feature of life and usually has a serious purpose.

(2) Cartoons in the West have been associated with political and social matters for many years. In wartime, for example, they proved to be an excellent way of spreading propaganda. Nowadays cartoons are often used to make short, sharp comments on politics and governments as well as on a variety of social matters. In this way, the modern cartoon has become a very powerful force in influencing people in Europe and the United States.

(3) Unlike most American and European cartoons, however, many Chinese cartoon drawings in the past have also attempted to educate people, especially those who could not read and write. Such cartoons about the lives and sayings of great men in China have proved extremely useful in bringing education to illiterate and semi-literate people throughout China. Confucius, Mencius and Laozi have all appeared in very interesting stories presented in the form of cartoons. The cartoons themselves have thus served to illustrate the teachings of the Chinese sages in a very attractive way.

(4) In this sense, many Chinese cartoons are different from Western cartoons in so far as they do not depend chiefly on telling jokes. Often, there is nothing to laugh at when you see Chinese cartoons. This is not their primary aim. In addition to commenting on serious political and social matters, Chinese cartoons have aimed at spreading the traditional Chinese thoughts and culture as widely as possible among the people.

(5) Today, however, Chinese cartoons have an added part to play in spreading knowledge. They offer a very attractive and useful way of reaching people throughout the world, regardless of the particular country in which they live. Thus, through cartoons, the thoughts and teachings of the old Chinese philosophers and sages can now reach people who live in such countries as Britain, France, America, Japan, Malaysia or Australia and who are unfamiliar with the Chinese culture.

(6) Until recently, the transfer of knowledge and culture has been overwhelmingly from the West to the East and not vice versa. By means of cartoons, however, publishing companies in Taiwan, Hong Kong and Singapore are now having success in correcting this imbalance between the East and the West.

(7) Cartoons can overcome language barriers in all foreign countries. The vast increase in the popularity of these cartoons serves to illustrate the truth of Confucius’s famous saying “One picture is worth a thousand words.” 

The major differences between Chinese cartoons and Western cartoons come from their __.

A. purposes         

B. styles      

C. values     

D. nationalities 

Mark the letter A, By Cy or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

We spend about one-third of our lives sleeping. We know relatively little about our sleep.

A. We shall know more about our sleep if we spend more than one-third of our lives sleeping

B. We know relatively little about our sleep; as a result, we spend about one-third of our lives sleeping

C. Despite spending about one-third of our lives sleeping, we know relatively little about our sleep

D. We spend about one-third of our lives sleeping so that we know relatively little about our sleep

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

Scientists have uncovered a new threat to the world's endangered coral reefs. They have found that most are incapable of growing quickly enough to compensate for rising sea levels triggered by global warming. The study suggests that reefs - which are already suffering serious degradation because the world's seas are warming and becoming more acidic - could also become overwhelmed by rising oceans.

The research - led by scientists at Exeter University and published in Nature this week -involved studying growth rates for more than 200 tropical western Atlantic and Indian Ocean reefs. It was found only 9% of these reefs had the ability to keep up with even the most optimistic rates of sea-level rises forecast by the Intergovernmental Panel on Climate Change. "For many reefs across the Caribbean and Indian Ocean regions, where the study focused, rates of growth are slowing due to coral reef degradation," said Professor Chris Perry, of Exeter University. “Meanwhile, rates of sea-level rise are increasing - and our results suggest reefs will be unable to keep up. As a result, water depths above most reefs will increase rapidly through this century.”

Sea levels rose by several inches over the past century and measurements indicate the speed of this increase is now rising significantly. Two key factors are involved: climate change is making ocean water warmer and so it expands. And as ice sheets and glaciers melt, they increase amounts of water in the oceans.

At the same time, reefs are being weakened by ocean warming and also by ocean acidification, triggered as the seas absorb more and more carbon dioxide. These effects lead to bleaching events that kill off vast stretches of coral and limits their ability to grow.

“Our predictions, even under the best case scenarios, suggest that by 2100, the inundation of reefs will expose coastal communities to significant threats of shoreline change,” said co-author Prof Peter Mumby of Queensland University. This point was backed by US marine scientist Ilsa Ruffner writing in a separate comment piece for Nature. “The implications of the study are dire. Many island nations and territories are set to quickly lose crucial natural resources.”

The author implies in the last paragraph that _______.

A. even in the most optimistic prediction, coral reefs will experience their extinction.

B. the results of the study are more serious than what scientists have predicted.

C. human activities will not only affect marine life but also put themselves at risk.

D. people often exploit natural resources in island nations and territories.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 30 to 34.

As heart disease continues to be the number-one killer in the United States, researchers have become increasingly interested in identifying the potential risk factors that trigger heart attacks. High-fat diets and „life in the fast lane” have long been known to contribute to the high incidence of heart failure. But according to new studies, the list of risk factors may be significantly longer and quite surprising.

Heart failure, for example appears to have seasonal and temporal patterns. A higher percentage of heart attacks occur in cold weather, and more people experience heart failure on Monday than on any other day of the week. In addition, people are more susceptible to heart attacks in the first few hours after waking. Cardiologists first observed this morning phenomenon in the mid-1980s and have since discovered a number of possible causes. An early-morning rise in blood pressure, heart rate, and concentration of heart-stimulating hormones, plus a reduction of blood flow to the heart, may all contribute to the higher incidence of heart attacks between the hours of 8:00 A.M and 10 A.M.

In other studies, both birthdays and bachelorhood have been implicated as risk factors. Statistics reveal that heart attack rates increase significantly for both females and males in the few days immediately preceding and following their birthdays. And unmarried men are more at risk for heart attacks than their married counterparts. Though stress is thought to be linked in some way to all of the aforementioned risk factors, intense research continues in the hope of further comprehending why and how heart failure is triggered.

What does the passage mainly discuss?

A. cardiology in the 1980s 

B. risk factors in heart attacks 

C. diet and stress as factors in heart attacks 

D. seasonal and temporal patterns of heart attacks

Read the following passage and blacken the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

        The history of clinical nutrition, or the study of the relationship between health and how the body takes in and utilizes food substances, can be divided into four distinct eras: the first began in the nineteenth century and extended into the early twentieth century when it was recognized for the first time that food contained constituents that were essential for human function and that different foods provided different amounts of these essential agents. Near the end of this era, research studies demonstrated that rapid weight loss was associated with nitrogen imbalance and could only be rectified by providing adequate dietary protein associated with certain foods.

       The second era was initiated in the early decades of the twentieth century and might be called “the vitamin period.” Vitamins came to be recognized in foods, and deficiency syndromes were described. As vitamins became recognized as essential food constituents necessary for health, it became tempting to suggest that every disease and condition for which there had been no previous effective treatment might be responsive to vitamin therapy. At that point in time, medical schools started to become more interested in having their curricula integrate nutritional concepts into the basic sciences. Much of the focus of this education was on the recognition of deficiency symptoms. Herein lay the beginning of what ultimately turned from ignorance to denial of the value of nutritional therapies in medicine. Reckless claims were made for effects of vitamins that went far beyond what could actually be achieved from the use of them.

        In the third era of nutritional history in the early 1950's to mid-1960's, vitamin therapy began to fall into disrepute. Concomitant with this, nutrition education in medical schools also became less popular. It was just a decade before this that many drug companies had found their vitamin sales skyrocketing and were quick to supply practicing physicians with generous samples of vitamins and literature extolling the virtue of supplementation for a variety of health-related conditions. Expectations as to the success of vitamins in disease control were exaggerated. As is known in retrospect, vitamin and mineral therapies are much less effective when applied to health-crisis conditions than when applied to long-term problems of under nutrition that lead to chronic health problems.

The word “skyrocketing” is closest in meaning to_________.

A. internationally popular

B. increasing rapidly

C. acceptable

D. surprising