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

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

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

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

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

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

 7. The dictionary is very        (help) to me.

8. Who is         (popular) teacher in your school?

9. I will go to the park if it        (not rain)tomorrow.

10. She spent half an hour        (do) the work yester day.