There’s no way of knowing why one man makes an important discovery __________ another man, also intelligent, fails.
A.while B.when C.where D.why
Jack was working in the lab __________ the power cut occurred.
A.suddenly B.which C.while D.when
Since we haven’t gone very far, we might just __________ well turn around to get the map.
A.for B.with C.in D.as
From time to time, our biology teacher tells us the only way he thinks of __________ experiments well is to practice.
A.do B.to do C.doing D.did
The president said if terrorists declared war __________ the United States, war would be what they got.
A.against B.on C.to D.for
The child was found __________ the streets alone.
A.wandered B.to wander C.wander D.wandering
