--Who is the old man talking with your teacher?
---I don’t know. I him before.
| A．was never seeing | B．had never seen | C．never saw | D．wouldn’t see |
---I hear Liza and her husband have flown to Hawaii for their honeymoon．
---Oh, how nice! Do you know when they?
| A．were leaving | B．had left | C．have left | D．left |
Be careful when you deal with this chemical, as it will explode when ______ to sunlight.
| A．exposed | B．to expose | C．exposing | D．being exposed |
Normally, a forest fire and the damage ______ causes can be very severe, especially when you consider the financial and physical losses.
| A．which | B．it | C．this | D．that |
---Sunday is a public holiday, _____children should get close to nature.
---But most of them have several lessons to attend.
| A．when | B．which | C．where | D．what |
If you had seen a doctor, you much better now.
| A．are | B．will be | C．would be | D．would have been |