请教：2016英语专八改错练习题二十二第7小题如何解答？

of nature of all insects are good, but if they are killed, things __8__go out of kilter right away.”

Developed in 1939, it first distinguished itself during the World War II, cleaning __3__

on DDT being conducted not far from which she lived in Maryland. __10__

Another was Rachel Carson, who wrote to the Reader’s Digest to propose an article about series of __9__tests

South Pacific islands of malaria-caused insects for U.S. troops, while __4__in Europe being used as an effective de-lousing power.

tiveness is limited to destroy one or two types of insects, DDT is __2__capable of killing hundreds of different kinds at once.

DDT, the most powerful pesticide the world had ever known,exposed nature’s vulnerability. Unlike most pesticides, which effect- __1__

When DDT became available for civilian use in 1945, there were only a few people who expressed the second thought about this __6__new miracle compound.

Even earlier in __2__1000 B.C.