根据句意和汉语注释，在答题卡标有题号的横线上，写出单词的正确形式。

1. Mr. Wu is our teacher. He teaches _____ (we) English.

2. Smoking is bad to people's _____ (healthy).

3. He likes swimming. He is a good _____ (swim).

4. The boy eats too many chocolates and sweet food, so his _____ (tooth) are getting worse.

D/A转换路是（）。

A.将输入量转换为输出量的电路

B.将数字量转换为模拟量的电路

C.将模拟量转换为数字量的电路

D.将模拟量转换为输入量的电路