问题补充:
He is rather difficult to make friends with, but his friendship, is more true than anyone else’s.
A. Once gaining
B. Once gained
C. Once is gaining
D. Once he gained
答案:
A. Once gaining
(答案→)B. Once gained
C. Once is gaining
D. Once he gained
解析:这题考察条件状语从句,当主从句的主语一致时,可以省略从句的主语和be动词,once gained=once his friendship is gained,选B。