you turn off all the lights when you leave the classroom．
| A．Making sure | B．To make sure | C．Being sure | D．Make sure |
salt
| A．almost | B．calm | C．chalk | D．half |
singer
| A．single | B．language | C．stronger | D．bringing |
realize
| A．pyramid | B．responsibly | C．whisper | D．title |
The book, ___________ is green, has been lent to my brother.
| A．of which cover | B．the cover of which | C．whose covers | D．its cover |
It is careless _______ such a mistake.
| A．of you to make | B．of your making | C．for you to make | D．for your making |