填词完成句子，首字母已给出。

1. L_____ Sunday I went to visit my uncle.

2. Li Ping is studying for the math t_____.

3. The math problem is a l_____ difficult. I can't work it out.

4. The teacher told me to s_____ at school, because I talked in class.

5. He is thirteen. He is a m_____ school student.

使用时发电机应放在空气流通的地方启动，可以在密室中启动发电机，以免导至昏迷或死亡。