The middle-aged scientist who( )abroad for 20 years by the end of next month,is on the way back to
问题描述：
The middle-aged scientist who( )abroad for 20 years by the end of next month,is on the way back to
his mothland.
A.had been B.is staying C.will have been D.will stay
答
首先不是虚拟语句,那主从保持时态一致,后面的谓语从句是现在时,那主句必须也是现在时.然后是到下个月才满20年,就是将来完成.C