4. My train arrives in New York at eight o'clock tonight. The plane I would like to take 　from there _____ by then.
A. would leave
B. will have left
C. has left
D. had left

6. It's reported that by the end of this month the output of cement in the factory ______ by about 10%.
A. will have risen
B. has risen
C. will be rising
D. has been rising

答案：
4. B
译文：我乘坐的火车今晚8 点到达纽约。那时我要在此搭乘的飞机将已起飞了。
本句是将来完成时的用法。句中“would like to … ”并不表示过去将来，而是表示一种意愿、愿望。到将来某时(by then)之前已完成的动作(leave) ，所以用将来完成时。