The scientist _____ Canada and he will give us a talk when he _____ back.
问题描述：
The scientist _____ Canada and he will give us a talk when he _____ back.
A.has gone to/comes B.has been to/will come
C.has gone to/will come D.has been to/comes
答
A,他已经去了加拿大,当他回来是用一般现在时的