It was never clear
The field research will take Joan and Paul about five months; it will be a long
time ____ we meet them again.
| A．after | B．before | C．since | D．when |
1 won’t call you, ________ something unexpected happens.
| A．unless | B．whether | C．because | D．while |
The manager suggested an earlier date ____________ the meeting.
| A．on | B．for | C．about | D．with |
I _____ it as a basic principle of the company that suppliers of raw materials should be given a fair price for their products.
| A．make | B．look | C．take | D．think |
Small sailboats can easily turn over in the water ______ they are not managed carefully.
| A．though | B．before | C．until | D．if |