用所给词的适当形式填空。 1. Our headmaster invited a
题型：填空题
问题：
用所给词的适当形式填空。
1. Our headmaster invited a singer ________ (sing) for us this morning.
2. I _______ (clean) my room at 9:00 last Sunday.
3. They can do that thing by ________ (they).
4. I think _______ (predict) the future is a bit difficult.
5. The teacher told us that light ________ (travel) much faster than sound.