问题

.They were __________ to produce carbon,nitrogen,water and other gases
A:in time
B:at a time
C:at one time
D:on time
B:at a time
C:at one time
D:on time
正确答案是:
同类题型
Can you tell me what to wear at the party —If I ___you,I___the blue jeans.
This is ___________ family photo.
When I got back home I saw a message pinned to thedoor ______“Sorry to miss you; will call later.”
A couple of years ________ since the earthquake took place in Wenchuan.
In the flood, about ________ people were injured and ________ houses fell into pieces.