First listen and then answer the following question. 听录音，然后回答以下问题。
How much of each year do spiders spend killing insects?
Why, you may wonder, should spiders be our friends? Because they destroy so many insects, and insects include some of the greatest enemies of the human race. Insects would make it impossible for us to live in the world; they would devour all our crops and kill our flocks and herds, if it were not for the protection we get from insect-eating animals. We owe a lot to the birds and beasts who eat insects but all of them put together kill only a fraction of the number destroyed by spiders. Moreover, unlike some of the other insect eaters, spiders never do the harm to us or our belongings.
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 insect never more than six.
How many spiders are engaged in this work no our behalf? One authority on spiders made a census of the spiders in grass field in the south of England, and he estimated that there were more than 2,250,000 in one acre; that is something like 6,000,000 spiders of different kinds on a football pitch. 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 spiders in Britain in one year would be greater than the total weight of all the human beings in the country.
T. H. GILLESPLE Spare that spider from The Listener
New words and expressions beast n. 野兽 census n. 统计数字 acre n. 英亩 content adj. 满足的
1、Why should...?形式的疑问句往往用来表示“不能理解”的含意。 A:Give me money.给我钱 B:Why should I?凭什么？
2、关系代词与关系从句 关系代词：通常起到连接复合句中的关系从句与主句的作用，引导关系从句，说明被修饰的名词或代词同该关系从句之间的关系。 关系从句：通常起形容词作用。它以一个短语的形式，置于名词或代词之后修饰该名词或代词。 （1）充当主语 He is the man who /that lives next door. （2）充当宾语 Hi is the man whom/that I met.
习题
1、Spiders are active in killing insects ______ A. all the time. B. for most of the year C. in the summer months D. for a minimum of six months of each year.
答案：D
2、We owe ______ to the birds and beast who eat insects. A. a great deal B. a lot of C. a great many D. much of
答案：A
3、You can see at a glance that spiders are not ______ insects. A. similar B. like to C. as D. ths same as