The field research will take Joan and Paul about five months; it will be a long time we meet them again.
A. after
B. before
C. since
D. when
网友回答
A. after
(答案→)B. before
C. since
D. when
解析：before引导时间状语从句。It will be a long time before…的意思是“要过很久才会……”，如：It will be a long time before we finish this dictionary. 我们需要很长的时间才能把这部词典编完。It was a long time before I got to sleep again. 过了好久我才又睡着。