Spiders are not insects, as many people think, nor even nearly related to them. One can tell the difference almost at a glance, for a spider always has eight legs and an insect never more than six.
How many spiders are engaged in the work on our behalf (利益)? One authority(权威人士)on spiders made a research on spiders and found that there were more than 2,250,000 in one acre (英亩); that is something like 6,000,000 spiders of different kinds on a football field. Spiders are busy for at least half the year in killing insects. It is impossible to make more than the wildest guess at how many they kill, but they are hungry creatures, not content with only three meals a day. It has been estimated that the weight of all the insects destroyed by the spiders in Britain in one year would be greater than the total weight of all human beings in the country.
40. Spiders should be our friends, because __________.
A. they only eat harmful insects
B. they are great insect-eating animals
C. they destroy large numbers of insects which do harm to the human race
D. their harmfulness is the least
41. One authority on spiders estimated ________.
A. that there were more than 2,250,000 insects in a grass field in the south of England
B. that every football field in England had 6,000,000 spiders.
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2016-02-29
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