-- Tommy, your mum has been out without glasses!
-- Well, take it easy. she is back home for them.
A. It is long before that
B. It won't be long since
C. It won't be long before
D. It will be long before
网友回答
A. It is long before that
B. It won't be long since
(答案→)C. It won't be long before
D. It will be long before
解析：考查句型：It will be +一段时间+before…,要多长时间才…，句意：--Tommy，你妈妈没带眼镜就出去了，没关系，不要多久她就会回来拿的。选C。