Scientists have spent years researching into the （） of sleeping pills on the human brain .

Many scientists have been probing psychological problems.

A．solving

B．exploring

C．settling

D．handling

The scientists have made an______study of the viruses that cause the disease.

A．exhausted

B．exhausting

C．exhaustive

D．exhaustion

Scientists have made great contributions()development of our human beings.

A. to

B. on

C. with

Even talented scientists have no way to precisely forecast the future. (英译汉)

ct)

A.far

B.farther

C.much

D.far more

With the population explosion, scientists will have to() new methods of increasing the worlds food supply.

A.lead to

B.carry out

C.come up with

D.stick to

A.affect

B.effect

C.impact

D.influence