He is rather difficult to make friends with,but his friendship,＿ is more true than any othe...

题目

He is rather difficult to make friends with,but his friendship,＿ is more true than any othe...
He is rather difficult to make friends with,but his friendship,＿ is more true than any other.A.oncegained B.when to gain C.after gaining D.whilegaining 为什么不能选BCD而要选A?请分析选BCD错在哪里?

答案

A
friendship和gain是被动关系,只能考虑过去分词了. B本身就错误,没有这样用法.
C D 都差不多,gaining现在分词是表主动所以不考虑.
整句意为：很难和他交朋友,但是一旦获得他的友谊,其友谊比任何.都真