阅读下列短文，从每题所给的四个选项A、B、C和D中，选出最佳选项。

　　Through a series of experiments an American scientist has obtained an understanding of the social structure of the most complex (复杂) of ant

　　societies. The ants examined are the only non--human creatures to have given up hunting and collecting for a completely agricultural way of life. In their underground nests they cultivate(耕作) gardens on soil made from finely chopped leaves. This is a complex operation requiring considerable division of labor. This type of ant workers can be divided into four groups according to size. Each of the groups performs a particular set of jobs.

　　The making and care of the gardens and the nursing of the young ants are done by the smallest workers. Slightly larger workers are responsible(负责) for chopping up leaves to make them suitable for use in the gardens and for cleaning the nest. A third group of still larger ants do the construction work and collect fresh leaves from outside the nest.

　　To find out how good the various size-groups are at different tasks, the scientist measured the amount of energy they used. He examined first the gathering and carrying of leaves. He selected one of the size-groups, and then measured how efficiently (有效) these ants could find leaves and run back to the nest. Then he repeated the experiment for each of the other size-groups. In this way he could see whether any group could do the job more efficiently than the group normally undertaking(从事) it.

　　The intermediate-sized (中间的) ants that normally perform this task proved to be the most efficient for their energy costs, but when the scientist examined the whole set of jobs performed by each group of ants it appeared that some sizes of worker ant were not suited to the particular jobs they performed.

1．In which way are ants different from non--human societies?

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A．They do not need to search for food

B．They do not need to look for shelter (隐蔽处).

C．Individuals (个人) are different in social positions.

D．Individuals perform different functions.

2．It seems that the smallest ants perform more of the ________.

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3．The organization of the ants has the effect of ________.

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A．getting the most work done

B．dividing the work up systematically

C．each ant helping with all the tasks

D．each ant doing what it can do best

4．We know from the passage that ________.

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A．an ant society divides tasks among them the most scientifically

B．everyone can do everything well

C．just like our human society, it is hard to make the best use of each person's ability

D．a big-sized individual must be of greater strength and works more efficiently