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  3. Through a series of experiments an American scientist has obtained an understanding of the social structure of the most complex

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

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问题    Through a series of experiments an American scientist has obtained an understanding of the social structure of the most complex of ant societies. The ants examined are the only creatures other than man to have given up hunting and collecting for a completely agricultural way of life. In their underground nests they cultivate gardens on soil made from finely chopped leaves. This is a complex operation requiring considerable division of labor. The workers of this type of ants 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 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. The largest are the soldier ants, responsible for defending the nest.
   To find out how good the various size-groups are at different tasks, the scientist measured the amount of work done by the ants against 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 these ants could find leaves and nm 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 it.
   The intermediate-sized 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 ants were not ideally suited to the particular jobs they performed.
The scientist’s work was based on _______.
选项 A、occasional observations
B、systematic observations
C、observations of several nests
D、observations of undisturbed nests
答案B
解析 综观全文，文章第一段指出：科学家注意到蚂蚁是除人之外的惟一已放弃狩猎和采集食物过着完全农业生活方式的生物；第二段指出科学家对蚂蚁按个体大小进行的分工情况进行研究；第三段介绍了科学家对蚂蚁的工作效率的研究；最后一段指出科学家研究发现蚂蚁社会中也存在分工不合理的现象。由此可看出科学家对蚂蚁的研究是系统的。故选[B]。
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