It is strongly ______ that the machines should be checked every year.
| A．recognized | B．recommended |
| C．recorded | D．recovered |
It’s really difficult to ______ what he is trying to express.
| A．leave out | B．break out | C．put out | D．make out |
We all felt a sense of ______ when we saw so many overseas Chinese coming back safe and sound from Libya.
| A．security | B．relief | C．emergency | D．achievement |
Scientists say it may be five years ______ it is possible to test this medicine on human patients．
| A．since | B．until | C．before | D．when |
Last month, the Japanese government expressed their thanks for the aid they ______ from China.
| A．receive | B．had received | C．have received | D．are receiving |
If you _____ smoke, please go outside because this is a non-smoking office.
| A．must | B．should | C．can | D．may |