A
涉及到语法项目"状语从句的省略"
如果状语从句中的主语和主句的主语一致且含有动词be,可省略从句的主语和be.
eg:He won’t attend the party unless (he is) invited.
Although (she is) not strong herself,the little girl tries her best to help others.
遇到这类题把省略的部分加上就会做了.