When_____they____(put up)these signs?

问题描述:

When_____they____(put up)these signs?

When do they put up these signs? 意思是他们什么时候捡起来这些广告牌.
这道题前面考的应该是区别do and does
后面考的应该是不定式吧,毕业太多年了,仅供参考.