-Someone’s knocking at the door. Is it your mother?
-No, dad. It _____be mom. I saw mom ____in the bedroom just now.
| A．must, sleep | B．may, sleeping |
| C．needn’t, sleep | D．can’t , sleeping |
They waited and waited, and_____ he came back.
| A．at once | B．at first |
| C．at the end | D．at last |
---It was ___________ who helped us out of danger.
---What brave and helpful children! We should learn from them.
| A．they | B．them | C．their | D．theirs |
My mother was doing the cleaning in the sitting room ________ the telephone rang.
| A．when | B．while | C．since | D．as soon as |
Every day, too much water _______ in our school. We should save it.
| A．is wasted | B．wastes |
| C．was wasted | D．wasted |