1.Only when the research has been carried out______whether the drug has a side effect on human body.

1.Only when the research has been carried out______whether the drug has a side effect on human body.
A.we decide B.we will decide C.did we decide D.will we decide
2.It was not until ge explained the reason _____we realized that we had misunderstood him
A.why B.which C.that D.whether
3.-Chemistry can help solve the pollution .What about math?
-_______.But you must admit that we can't study chenmistry without math
A.Never mind B.It's hard to say
C.Cheer up D.Well done.