.Having checked the doors were closed, and _____all the lights were off, the boy opened the door to his bedroom.
| A．why | B．that | C．when | D．where |
______ the sight was impressive on the top of the mountain, I made an effort to climb onto it.
| A．To know | B．Know | C．Known | D．Knowing |
We still have some other ways to solve the problem. You ______ be worried.
| A．mustn’t | B．can’t |
| C．don’t have to | D．may not |
Harry Potter has made reading popular again, ______ is why parents and teachers like the book, too.
| A．that | B．who | C．which | D．what |
Some countries have banned smoking in public places ______ public health.
| A．improve | B．to improve |
| C．improving | D．improved |
Mr. Smith had to go to work by bus this morning as his car ______.
| A．would repair |
| B．was repairing |
| C．had been repaired |
| D．was being repaired |