Question

Mrs. White became a teacher in 1985. She _____ for twenty years by next summer.

A．will teach

B．would have taught

C．has been teaching

D．will have been teaching

Answer 1

D解析:
语境中的时间信息：by next summer  到明年夏天，提示该题应为将来时，故排除B、C。 根据句意：怀特夫人自1985年成为教师，到明年夏天就将教书法家20年了。因此，只有将来完成进行时才能表示这个将来某时前一直进行的动作。故选择D。