括号中所给动词的正确形式填空。 1. It's five o'clock. The students ________ (play) football on the playground. 2. You _______ (not pass) the exam if you don't work hard enough. 3. The baby is sleeping. Could you please stop ________ (make) so much noise? 4. This machine ________ (use) for cleaning the house. 5. The man spoke very slowly. He wanted me ________ (understand) what he said.