问题补充：
--- Do you love teaching, Miss He?
--- I fell in love with teaching in 2000. I for twelve years by this summer.
A. will teach
B. would have taught
C. has been teaching
D. will have been teaching
答案：
A. will teach
B. would have taught
C. has been teaching
(答案→)D. will have been teaching
解析：考查时态。本题的关键词是by, By与完成时连用。当by后面是过去的时间，使用过去完成时；当by后面是现在的时间，使用现在完成时，当by后面是将来的时间的时候，使用将来完成时。本题的By后面使用的是this summer这个将来的时间，故使用将来完成时，本句指教书这个动作持续到现在，故使用进行时的形式。故D正确。
