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.

An air pollutant is defined as a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled - a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.

Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentration of these pollutants was altered by various chemical reactions; they became components in biogeochemical cycles. These serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature's output of these compounds dwarfs that resulting from human activities.

However, human production usually occurs in a localized area, such as a city. In such a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact, the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area.

The word "adversely" in the first paragraph is closest in meaning to _______.

A. negatively

B. quickly

C. admittedly 

D. considerably

Thuốc thử thích hợp để nhận biết 5 dung dịch đựng trong 5 lọ riêng biệt Na₂CO₃, AgNO₃, NaCl, NaBr, NaI là

A. HCl

B. Pb(NO₃)₂

C. AgNO₃

D. Cả A và C đều đúng

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 1 to 8.

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-1980, 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 10:00 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.

The word "potential" could best be re-placed by which of the following?

A. harmful

B. primary

C. unknown

D. possible

Hiện tượng tiếp hợp trao đổi đoạn không cân giữa các NST tương đồng trong Giảm phân có thể dẫn tới hiện tượng đột biến cấu trúc NST nào sau đây:

A. Đột biến chuyển đoạn

B. Đột biến mất đoạn

C. Đột biến lặp đoạn

D. Đột biến mất đoạn, lặp đoạn

Gọi S là tập hợp những điểm biểu diễn số phức z thỏa mãn  z - i - 1 = 1   . Cho P là một điểm chạy trên S. Khi đó số phức tương ứng với P có môđun lớn nhất bằng ?

B. Không lựa chọn nào đúng