问题补充：
he will leave for Beijng.
A. It will not be long before
B. It is before long that
C. It is before long
D. It was before long that
答案：
A. It will not be long before
(答案→)B. It is before long that
C. It is before long
D. It was before long that
解析：这是一个强调句。强调部分是before long。
