Of all living creatures on earth, insects are the most plentiful. Some　 36　 are very useful to man, Of all living creatures on earth, insects are the most plentiful. Some 36 ____ are very useful to man, for example, bees, 37 ____ we get honey and wax, and silkworms, which 38 ____ us with silk. Other varieties, 39 ____, are extremely harmful, and do a great 40 ____ of damage, especially to crops. Locusts （蝗虫） are perhaps the most dangerous of all, 41 ____ they will eat almost any green 42 ____ , and when millions of them 43 ____ on cultivated land（耕地）they soon leave it 44 ____. In some countries they are the farmer’s 45 ____ enemy. Another nuisance is the common 46 ____ , not only because it 47 ____ us indoors and out - of- doors, but because it spreads diseases. Scientists have given much time and 48 ____ to the study of insects. It needs the most careful and 49 ____ observation. Thanks 50 ____ their discoveries we now know almost all 51 ____is to be known about the habits of these hardworking insects, bees and ants, which live in 52 ____better planned in some ways than our 53 ____ . But the most valuable work has been done in trying to give 54 ____ to men, animals and crops from the　 55　 which insects cause. 36．A. members  B. forms  C. qualities  D. varieties 37．A. by which  B. from which  C. of which  D. in which 38．A. give  B. produce  C. offer  D. supply 39．A. however  B. meanwhile C. therefore  D. what's more 40．A. majority  B. number  C. amount  D. quantity 41．A. and  B. for  C. if  D. when 42．A. grass  B. field  C. fruit  D. plant 43．A. settle  B. attack  C. pass  D. cross 44．A. bare  B. nothing  C. empty  D. untouched 45．A. hardest  B. greatest  C. serious  D. wildest 46．A. insect  B. creature  C. fly  D. enemy 47．A. dislikes  B. bites  C. worries  D. hates 48．A. understanding  B. ideas  C. comprehension  D. thought 49．A. serious  B. patient  C. curious  D. long 50．A. for  B. of  C. to  D. with 51．A. that  B. which  C. there  D. what 52．A. societies  B. crowds C. teams  D. organizations 53．A. world  B. nation  C. selves  D. own 54．A. help  B. protection  C. living  D. defense 55．A. injury  B. wound  C. sickness  D. ruin