Mother told her son that it would be half a year she could come back from American.A. sin

问题补充：

Mother told her son that it would be half a year she could come back from American.

A. since

B. before

C. that

D. when

答案：

A. since

(答案→)B. before

C. that

D. when

解析：考查连词。固定句型：It be 一段时间before从句；意为：一段时间以后某事在发生。句意：妈妈告诉她的儿子，半年以后她才会从美国回来。