✔ 最佳答案
Think about the following examples:
1. Do you speak French?
2. Does he want pizza?
3. Are you Chinese?
4. Is he smart?
You will not use the other way. Because we use the form of DO; as helping verb in the question to help the main verb. Like Q1 & Q2. the main verbs are SPEAK & WANT;. So, your answer should be: Yes, I speak French; or Yes, I do. and Yes, he wants; or No, he doesn't want.
For the form of BE; is/am/are/was/were. No helping verb is needed in question and we can just simply reverse the position of the subject and the verb form of "be". The answer for Q3 is Yes, I am Chinese. For Q4; Yes, he is smart.
Or you can use the form of BE; in question like the following:
1. Are they playing tennis?
2. Is she working?
See, the changes of the main verb? PLAY and WORK, we need to use v+ing when using is/am/are as helping verb in a question.