根据句意及单词首字母完成单词。

1. It's raining heavily outside. Please take an u_____ .

2. When I left my home, I forgot to say “G_____"to my parents.

3. Tom looked t_____his paper before he handed it in.

4. We use the e_____to go up and down the building.

5. You can buy books in the b_____ .