不一定
1）除了用do,根据需要还可以用can ,could,will等等情态动词加行为动词
例如：what can you see in the sky?
2）who 引导的疑问句就不用加do
例如：who made this cake?
3）这些疑问词用在从句中,就不加do
例如：I don't know how to get along with him.
you should remember what you learn.