did your uncle leave his home town?.Let me see. He for nearly twenty years.A. Wh

问题补充：

--- did your uncle leave his home town?.

--- Let me see. 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：

A. When; has left

(答案→)B. When; has been away

C. How long; has left

D. How long; has been away

解析：句意：你的叔叔什么时候离开了他的家乡？——让我想想。他已经离开将近二十年了。结合语境可知上文描述的是过去发生的动作，故用一般过去时态。下文描述的是从过去一直持续到现在的动作，故用现在完成时态。瞬间动词不能和表示一段时间的时间状语连用，leave表示瞬间动作，故选B。