He was told that it would be at least three more monthshe could recover and return to work

问题补充：

He was told that it would be at least three more monthshe could recover and return to work.

A. when

B. before

C. since

D. that

答案：

A. when

(答案→)B. before

C. since

D. that

解析：before引导时间状语从句，意为“在……之前”，表示他康复重返工作还至少三个月时间。when引导时间状语从句，意为“当……的时候”。since引导时间状语从句，意为“自从”，表示从某个时候一直延续到现在，常与现在完成时连用。that用于名词性从句或定语从句。