按要求填空。

1. I like French fries. It is ______(west) food.

2. "I" ______(be) a letter.

3. I like ______(go) to the market.

4. ______ (not) do your homework now.

屏障设施实验动物饲育室为了保持（），注意定期更换风机的空气过滤器。