ng臭氧(O3)中有m个氧原子,则阿伏伽德罗常数NA的数值可表示为 [ ]
A.n/16m
B.n/48m
C.16m/n
D.48m/n
答案:C
Speaking of all the songs he has written, I think this is probably his __________ one.
A.better-known
B.well-known
C.best-known
D.most-known
— Why did they walk home yesterday?
— Because they ____ all their money. [ ]
A.spent
B.have spent
C.had spent
D.would spend