用所给词的正确形式填空。

1. The Great Wall as well as the Palace Museum ___________ (attract) lots of tourists from abroad every year.

2. If those wild animals can't find enough food, they ___________ (die) or have to leave their habitat soon.

3. The law of gravity ____________ (discover) by Isaac Newton about 350 years ago.

4. You must try your best to stop him ____________ (make) the same mistake again.

5. As soon as he came into the office, he ____________ (shake)hands with every one of us.

6. Since last August, the old lady ____________ (have) bad headaches three to four times a month.

7. By 5:30 yesterday afternoon he ____________ (finish) writing the laboratory report.

8. Bangkok, the capital of Thailand, ____________ (know) as the "City of Angels".

9. We should do everything we can ____________ (protect) the environment.

10. Jack said he ____________ (return) the two books to the library in a week.