填入动词的适当形式。

1. Knives are used for _________ (cut) things.

2. Can you finish __________ (read) the book in three days?

3. The doctor was busy __________ (operate) on the boy at that time.

4. Stop _________ (talk) and listen to me carefully.

5. Thank you very much for _________ (help) us.

6. Granny is very ill and she doesn't feel like _________ (eat) anything.

7. The girl enjoys _________ (listen) to light music.

8. Do you remember _________ (buy) me a beautiful skirt on my 13th birthday?

9. We couldn't help _________ (laugh) after we heard the funny story.

10. What about __________ (go) out for a walk?

请解释ATM网络的拥塞概念、出现拥塞的原因。