用括号内所给单词的适当形式填空

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.

教育学是一门以（）、教育问题为研究对象，探索（）的科学。