Many facts proved that long before Columbus ________ America, Chinese had visited it.
| A．noticed | B．uncovered | C．discovered | D．arrived |
The aged are close companions, and many of have known each other for decades.
| A．them | B．that | C．whom | D．what |
The job market has changed and ourto finding work must change as well.
| A．way | B．method | C．means | D．approach |
__________ the experiment right, I tried again and succeeded.
| A．Not having done | B．Having not done | C．Not doing | D．Not done |
---When shall we meet your cousin at the station?
---His plane took off 2 hours ago, and it _________ arrive at 5pm.
| A．could | B．should | C．must | D．can |
A lot of research and studies have shown that Trench oil, taken out from kitchen waste, ______ the increase of cancers.
| A．results from | B．attends to | C．contributes to | D．devotes to |