英语When (what）is the best time to come to Beijing?

题目

英语When (what）is the best time to come to Beijing?
When (what）is the best time to come to Beijing?
为什么when和what都能用?

答案

我认为应该用when更恰当些,当然,两个都可以用 .
意思是：什么时候最适合去北京?
to come to Beijing是表目的,也可以说是宾语补足语.