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 39 to 45.

Long before they can actually speak, babies pay special attention to the speech they hear around them. Within the first month of their lives, babies' responses to the sound of the human voice will be different from their responses to other sorts of auditory stimuli. They will stop crying when they hear a person talking, but not if they hear a bell or the sound of a rattle. At first, the sounds that an infant notices might be only those words that receive the heaviest emphasis and that often occur at the ends of utterances. By the time they are six or seven weeks old, babies can detect the difference between syllables pronounced with rising and falling inflections. Very soon, these differences in adult stress and intonation can influence babies' emotional states and behavior. Long before they develop actual language comprehension, babies can sense when an adult is playful or angry, attempting to initiate or terminate new behavior, and so on, merely on the basis of cues such as the rate, volume, and melody of adult speech.

Adults make it as easy as they can for babies to pick up a language by exaggerating such cues. One researcher observed babies and their mothers in six diverse cultures and found that, in all six languages, the mothers used simplified syntax, short utterances and nonsense sounds, and transformed certain sounds into baby talk. Other investigators have noted that when mothers talk to babies who are only a few months old, they exaggerate the pitch, loudness, and intensity of their words. They also exaggerate their facial expressions, hold vowels longer, and emphasize certain words.

More significant for language development than their response to general intonation is observation that tiny babies can make relatively fine distinctions between speech sounds. In other words, babies enter the world with the ability to make precisely those perceptual discriminations that are necessary if they are to acquire aural language.

Babies obviously derive pleasure from sound input, too: even as young as nine months they will listen to songs or stories, although the words themselves are beyond their understanding. For babies, language is a sensory-motor delight rather than the route to prosaic meaning that it often is for adults.

The word “diverse” in paragraph 2 is closest in meaning to _______. 

A. surrounding 

B. divided 

C. different 

D. stimulating 

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 55 to 64.

         Although they are an inexpensive supplier of vitamins, minerals, and high-quality protein, eggs also contain a high level of blood cholesterol, one of the major causes of heart diseases. One egg yolk, in fact, contains a little more than two-thirds of the suggested daily cholesterol limit. This knowledge has caused egg sales to plummet in recent years, which in turn has brought about the development of several alternatives to eating regular eggs. One alternative is to eat substitute eggs. These egg substitutes are not really eggs, but they look somewhat like eggs when they are cooked. They have the advantage of having low cholesterol rates, and they can be scrambled or used in baking. One disadvantage, however, is that they are not good for frying, poaching, or boiling. A second alternative to regular eggs is a new type of egg, sometimes called 'designer' eggs. These eggs are produced by hens that are fed low-fat diets consisting of ingredients such as canola oil, flax, and rice bran. In spite of their diets, however, these hens produce eggs that contain the same amount of cholesterol as regular eggs. Yet, the producers of these eggs claim that eating their eggs will not raise the blood cholesterol in humans.

         Egg producers claim that their product has been portrayed unfairly. They cite scientific studies to back up their claim. And, in fact, studies on the relationship between eggs and human cholesterol levels have brought mixed results. It may be that it is not the type of egg that is the main determinant of cholesterol but the person who is eating the eggs. Some people may be more sensitive to cholesterol derived from food than other people. In fact, there is evidence that certain dietary fats stimulate the body's production of blood cholesterol. Consequently, while it still makes sense to limit one's intake of eggs, even designer eggs, it seems that doing this without regulating dietary fat will probably not help reduce the blood cholesterol level.

According to the author, which of the following may reduce blood cholesterol?

A. decreasing egg intake and fat intake 

B. increasing egg intake and fat intake

C. reducing egg intake but not fat intake

D. increasing egg intake but not fat intake

Một quần thể có tần số kiểu gen ban đầu: 0,4AA : 0,2aa : 0,4Aa. Biết rằng các cá thể dị hợp tử chỉ có khả năng sinh sản bằng 1/2 so với khả năng sinh sản của các cá thể đồng hợp tử. Các cá thể có kiểu gen AA và aa có khả năng sinh sản như nhau. Sau một thế hệ tự thụ phấn thì tần số cá thể có kiểu gen dị hợp tử sẽ là

A. 12.5%.

B. 6,25%.

C. 50%.

D. 25%

Khi nói về hoán vị gen những phát biểu nào sau đây là chính xác?

Hoán vị gen là hiện tượng di truyền trong nhân chủ yếu của sinh vật Tần số hoán vị gen tỉ lệ nghịch với khoảng cách tương đối của các gen trên 1 NST Tần số hoán vị gen tỉ lệ thuận với khoảng cách tương đối của các gen trên 1 NST Hoán vị gen làm tăng tần số xuất hiện của biến dị tổ hợp cung cấp nguyên liệu cho tiến hóa và chọn giống Hoán vị gen đảm bảo tính ổn định cho loài qua nhiều thế hệ. Tần số hoán vị gen 0% < f ≤ 50%.

A. 1, 3, 4

B. 2, 3, 5

C. 1, 5, 6

D. 3, 4, 6

Trong những năm từ 1925 đến 1929, giai cấp công nhân có vai trò như thế nào trong phong trào dân tộc dân chủ ở nước ta?

A. Lãnh đạo duy nhất 

B. Nòng cốt

C. Quan trọng 

D. Phụ thuộc vào giai cấp khác

Một gen chứa 90 vòng xoắn, và có 20% Adenin. Đột biến điểm xảy ra dẫn đến sau đột biến, số liên kết hiđrô của gen là 2338. Dạng đột biến nào sau đây đã xảy ra?

A. Thêm một cặp A - T.

B. Mất 1 cặp G - X 

C. Thay 1 cặp A - T bằng 1 cặp G - X

D. Mất 1 cặp A - T