答案：C

　　B

　　In America these days，gardeners are starting to see more spiders in their gardens.Spiders kill more insects than they can eat，and most spiders can eat up to twice their body weight of insects each day.So，if you want to keep harmful insects out of your garden，you should invite a few spiders to live there.This was the advice given some years ago in the magazine Organic Gardening.Professor Susan Riechert at the University of Tennessee said that spiders eat more harmful insects than helpful ones.She said spiders will kill from sixty to eighty percent of the insects in a garden.She added，however，that “if you want spiders to live in your garden，you must not use chemicals that can kill them”.

　　Here are a few of the different kinds of spiders that live in gardens.Orb weaver spiders make huge sticky webs between plants.When an insect enters the web and is trapped，the spider attacks.Mesh­web weavers make tiny webs inside small openings in a plant's skin，Comb­footed spiders trap insects in their webs.When an insect lands on the web，the spider jumps out，catches the insect and drags it back inside the funnel (漏斗) to eat it.Wolf spiders do not use webs to trap insects.They live on the ground among the leaves.They eat aphids (蚜虫)，leafhoppers (叶蝉)，flies，beetles and grasshoppers.Jumping spiders do not make webs，either.Lynx spiders will spin (织) some silk to seize an insect，but they，too，do not make a web.They like to eat fire ants.Crab spiders move sideways，just like crabs in the sea.Crab spiders do not make webs.They wait quietly for an insect to come near and then they capture it.

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