Complete the sentences with a verb in the Present Perfect Continuous tense form.
| argue | do | increase | live |
| | ring | shout | study |
| surf | think | try | work |
1. I have been making a pie. That’s why my hands are all covered with flour.
2. His mobile … for fifteen minutes. I wonder why he doesn’t answer it.
3. He … extra hours. That’s why he looks so tired.
4. You … English for a year and don’t even know the alphabet!
5. We … about it for the past three hours and haven’t come to an arrangement yet.
6. You … at each other for over an hour. Perhaps you should stop now.
7. I … to upgrade my computer recently. I’ve spent a fortune!
8. You are shaking like a leaf. I wonder what you … .
9. He … in Seattle for a few months.
10. I … of buying a netbook lately.
11. The world population … very fast recently.
12. You … the Internet for the last four hours! Isn’t it time to stop?