There were two boys in the lab, did the experiment successfully.
17. Be when you cross the road.
16. You cannot be too careful. Which of the following sentences doesn’t have the same meaning of the underlined sentence? _____
15. In an emergency, you should remain _____.
14. It was a _____ evening and I really had a good sleep.
13. The foreman(工头) beat him _____ , and the other workers were very angry with him.