Only use ma(嗎) for yes-no questionsand not wh-questions(questions that ask what, why, when, where, who, and how).
- 這是水嗎? (Is this water?)
- 這是什麼? (What is this?)
Question 1 is a yes-no question, since it asks the hearer to answer yes or no to whether this is water. Question 2, on the other hand, is a wh-question, since it asks whatthis is, and therefore cannot come with ma(嗎).