Carbon dioxide, which makes a ______ between us and the sun, prevents heat from getting out of the atmosphere easily, so the earth is becoming warmer.
| A．difference | B．comparison | C．connection | D．barrier |
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 |
It is none of your business ________ other people think about you.Believe
yourself.
| A．how | B．what |
| C．which | D．when |
—Where's that report?
—I brought it to you ________you were in Mr.Black's office yesterday.
| A．if | B．when |
| C．because | D．before |
You can only be sure of ________ you have at present; you cannot be sure of something ________ you might get in the future.
| A．that; what | B．what; / |
| C．which; that | D．/; that |
Could I speak to ________ is in charge of International Sales，please?
| A．anyone | B．someone |
| C．whoever | D．no matter who |