Scientists have to work hard to keep _____ with modern discoveries and developments.
| A．company | B．track | C．touch | D．pace |
___________ your car unlocked outside means ___________ trouble.
| A．Leaving; to invite | B．Leaving; inviting |
| C．To leave; to invite | D．To leave; being inviting |
_________ to reach them on the phone, we sent an email instead.
| A．Fail | B．Failed | C．To fail | D．Having failed |
What shall human beings do if oilsometime in the future?
| A．will run out | B．runs out of | C．runs out | D．will be run out |
Chen Chunlong is a hero ofLiaocheng can be proud.
| A．who | B．whom | C．that | D．which |
It was not until mid-night_______ they reached the camp site.
| A．that | B．when | C．while | D．before |