I don't know why he isn't here.
举一反三
- He was here for a little while, but I don't know where she ( ) now. He was here for a little while, but I don't know where she ( ) now.
- I don’t know why you always ________ about the food here.
- I don’t know why he ________ in the middle of a sentence.
- I don’t know when he ________. When he _______ here, I’ll call you in a minute.
- I don't think he is serious,________ A: do I B: is he C: don't I D: isn't he