将来完成时用来表示在将来某一时间以前已经完成或一直持续的动作。经常与before 将来时间或by 将来时间连用，也可与before或by the time引导的现在时的从句连用。
【例如】
I will have finished all the work by the time you are back this evening.I am sure he will have left Paris by this time tomorrow.I hope we will have got all the information before you come tomorrow.By the end of this month, we surely____a satisfactory solution to the problem. (CET-4 1993, 6)
A) have found
B) will be found
C) will have found
D) are finding
本题时间状语为by 将来时间，考察将来完成时用法,应选择C.
The conference____a full week by the time it ends. (CET-4 1996, 6)
A) must have lasted
B) will have lasted
C) would last
D) has lasted
将来完成时用来可以表示在将来某一时间以前一直持续的动作，本句话的意思是：这次会议将持续整一周才结束，因此谓语动词用将来完成时，答案为B.