在横线上写出单词的正确形式。

1. There are some things that you can't change, like your               (身高).

2. The seats have no back ____________ (紧靠着)which to lean.

3. A space sleeping bag is used to be fixed to the walls to prevent__________(漂浮).

4. We must do something to deal with the ___________ (污染) water, otherwise, the fish will die.