Only when the war was over ________ return home．

A.he was able to

B.was he able to

C.could he be able to

D.would he be able

答案及解析： B

解析：

题意是“只有到战争结束，他才能回国”。主要考查only+连词(when/before/after/while)引导的状语从句的用法，倒装的是主句。C选项虽然是倒装，但用了could一般不再用be able to，D选项would he be able缺少to。根据句子结构故选B项。