It won’t be quite a long time your son is back so don’t be worried. A. that B. since C.

问题补充：

It won’t be quite a long time your son is back, so don’t be worried.

A. that

B. since

C. before

D. until

答案：

A. that

B. since

(答案→)C. before

D. until

解析：这题考查句型：It will be +一段时间+before。。。“要过多长时间才”，句意是：要不了多久 他儿子就回来了，所以别担心。选C。