Question

My parents have been to Beijing really. When ________ there.

1. A.
   will they go
2. B.
   did they go
3. C.
   had they gone
4. D.
   have they gone

Answer 1

B
现在完成时与一般过去时的区别典型题例：when和where一般不跟现在完成时连用，这句中的“去北京”这一动作是过去发生的，所以答案应为B。