吗 and question words provide different question patterns.
Introductory pattern#
Statement + 吗; sentence containing a question word
Worked teaching example#
你喝茶吗？你喝什么？
Do you drink tea? What do you drink?
Practise the distinction#
Compare the yes-or-no question with the request for information.
The example and exercise are newly written for this lesson. They do not report an event, interview or study. This introduction covers the displayed use, rather than all constructions involving the same words.
Reference#
Grammar reference. The reference supports the grammar point; no example sentence has been copied from it.