问题
选择题
---_____ did your uncle leave his hometown?
---He ________ for nearly twenty years.
A．When; has left
B．When; has been away
C．How long; has left
D．How long; has been away
答案
答案：B
第一空，因为后面给的动词是短暂性动词，所以用特殊疑问词when ，因为how long 与延续性动词连用，而后一个空，后接for+一段时间，所以特殊疑问词需要是延续性的，故选B