FOOD CHAINSOriginally the idea of a "food chain" was develop

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 questionsFOOD CHAINSOriginally, the idea of a "food chain" was developed by a scientist named Charles Elton in 1927. Elton described a general food chain in terms of where plantsand animals get their energy. He started with plants, which get energy from sunlight. Next, plant-eating animals get their energy from eating other plants. At the next level of the chain, meat-eating animals get their energy from eating other animals. Elton's idea of a "chain" related to the concept that all these animals are linked together by what they eat. Anything that affects one part of the chain affects all of the other parts in the chain. The first part of the chain, plants, is called the producer. All of the parts of the chain above the producer are called consumers.Here is a simple example of a food chain. Grass uses sunlight to produce sugars and proteins so that it can grow. Rabbits eat the grass and get energy from it. Foxes eat rabbits and get energy from them. Foxes are at the "top" of this food chain because nothing eats them. Now imagine that a farmer plows up the field of grass where the rabbits usually eat. Some of the rabbits might die. Others will probably move to another location to find food. In either case, there are fewer rabbits. This means less food for the foxes. Thus, the foxes depend on the grass in a way, even though they don't eat the grass directly.A In the natural world, of course, there are no simple food chains like this. Rabbits eat lots of plants besides grass. B Foxes eat lots of things besides rabbits. C Additionally, there are lots of other things in nature that eat grass and rabbits! DHowever, that does not mean the idea of a simple food chain is not important. Food chains are still a useful concept to consider, even if they are an oversimplification of reality. Take, for example, the case of DDT’s effect on animals. In the 1960s, DDT, a common pesticide at that time, was used a lot by farmers. Farmers only used a little at a time, so large animals were not harmed. However, once DDT was used in a field, it did not go away. Whenever it was used, DDT just stayed in the environment. Eventually, rain washed it into rivers and lakes. Plankton, a tiny water organism, absorbed the DDT. Then, fish ate the plankton. There was not much DDT in one bit of plankton, but small fish consumed many little bits of plankton. Then, larger fish ate lots of the smaller fish. So, the concentration of DDT in the larger fish became higher. Then, birds such as the osprey ate larger quatities of the larger fish.In the end, compared to the concentration of DDT in plankton, the concentration of DDT in osprey was 10 million times greater! The DDT did not kill the osprey, though. It just made the female osprey lay eggs with very thin shells. The shells were so thin that when the mother sat on the eggs, they broke. Thus the osprey population became greatly reduced before rebounding to today’s levels.

Câu 1: According to the passage, which of the following is true about Elton's idea of food chains?

A. He only looked at plants and animals near his home.

B. Other scientists at the time rejected Elton's idea.

C. The chains started with plants.

D. They measured the energy stored in food.

Câu 2: As used in paragraph 2, what is the meaning of the word "field"?

A. A piece of land for plants       

B. An area of study

C. A place for playing games   

D. A region that is visible

Câu 3: What does "others" in paragraph 2 refer to?

A. farmers     

B. food chains    

C. foxes

D. rabbits

Câu 4: In paragraph 3, what does the author imply?

A. Animals that do not eat other animals

B. How simple food chains are limited

C. The relationship of rabbits and foxes

D. Ways to teach food chains to children

Câu 5: Why does the author mention DDT in reference to food chains?

A. To compare this chemical's effect on producers and consumers

B. To explain why consumers sometimes become extinct

C. To illustrate the true complexity of nature

D. To show how the simple concept of food chains could be useful

Câu 6: Why did large fish in rivers and lakes have high concentrations of DDT in their bodies?

A.  The large fish ate small fish with DDT in them

B. The large fish laid eggs in plankton with DDT in it

C. The large fish naturally produced DDT

D. The large fish swam in water with DDT in it

Câu 7: Where would the following sentence best fit in the paragraph 3?
Therefore, when trying to describe the real world, it is more appropriate to think of food webs rather than food chains.

A. A

B. B

C. C

D. D