—Has your son come back from abroad for the winter vacation?

—Yes. But he stayed at home for only a week. Now he      back to college.

A．went

B．has gone

C．was going

D．will go

沉香来源于哪科植物( )

A．木通科

B．毛茛科

C．豆科

D．瑞香科

E．茜草科