用 did 提问时，动词要用原形

过去时疑问句用了 did，后面的主要动词必须用原形，不能再用过去式。did 已经表示过去了，所以不能写 thought，要用 think。

❌ What did you said?
✅ What did you say?
❌ What did he meant?
✅ What did he mean?