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.

          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. For example, sulfur dioxide has detectable health effects at 0.08 parts per million (ppm), which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.

The word "detectable" in the third paragraph is closest in meaning to _________ . 

A. measurable      

B. beneficial                   

C. special             

D. separable

Dưới đây là tháp sinh thái biểu diễn mối tương quan về sinh khối tương đối giữa động vật phù du và thực vật phù du trong hệ sinh thái đại dương:

Sinh khối của động vật phù du lớn hơn sinh khối của thực vật phù du bởi vì:

A. các động vật phù du nhìn chung có chu ky sống ngắn hơn so với thực vật phù du.

B. các thực vật phù du đơn lẻ có kích thước nhỏ hơn nhiều so với động vật phù du.

C. các thực vật phù du có tốc độ sinh sản cao và chu kỳ tái sinh nhanh hơn so với động vật phù du.

D. các động vật phù du chuyển hoá năng lượng hiệu quả hơn.

Mark the letter A,B,C or D on your answer sheet to show the underlined part that needs correction in each of the following question

(A) One of the students who (B) are being considered (C) for the scholarship (D) are from this university

A. One of

B. are being

C. for the

D. are

Read the following passage and mark the letter A, B, C or D to indicate the correct answer.

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 cholesterol limit. This knowledge has driven 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 eating 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 diet, 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 relationship between eggs and human cholesterol levels have brought mixed result. It may be that it is not the type of eggs 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 passage, egg substitutes cannot be used to make any of the following types of eggs EXCEPT ______.

A. boiled 

B. poached

C. scrambled

D. fried