根据人教新目标版九年级英语unit11《Could you please tell me where the restroom》完成下列句子，每空词数不限。

1. It is a very common and necessary activity to _____________.

2. Knowing _____________ is important.

3. We should change _____________we speak when talking with different people.

4. The expressions you use might depend on ___________ you are speaking to or __________ you 

    know them.

5. If you stop a stranger in the street, we might first say "Excuse me. __________" or "I'm sorry to 

    trouble you but," before asking them for help.