—Bob, how about having a picnic this weekend?
—________ I'll check my schedule.
| A．Sounds great. | B．Good idea. | C．I'm not sure. | D．Well done. |
.The other day I was showing the boys the weekly chemistry experiment when, ________ I knew it, the mixture was bubbling over everywhere.
| A．if | B．before | C．though | D．unless |
It was not until all the milu deer ________ that we realized we should build a natural park to protect them.
| A．died off | B．died away | C．died out | D．died down |
Do you remember a certain occasion ________ you were in trouble and at that moment I gave you a hand.
| A．when | B．which | C．why | D．where |
You may catch up with others__________you work a little harder.
| A．so long as | B．so far as | C．however | D．unless |
__________ the students are doing their maths exercises with the help of the teacher.
| A．Three score of | B．Three scores |
| C．Score of | D．Scores |