Mothers holding jobs outside the home should have ______ schedules to make it easier to care for their children.
| A．heavy | B．smooth | C．flexible | D．complex |
What is even more important is______ the earth cooled down, water began to appear on its surface.
| A．that | B．that as | C．which | D．which as |
His idea was such a good one ______ we all agreed to use it.
| A．as | B．that | C．so | D．but |
Although the causes of cancer_____, we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |
With just four years _______, the Brazil Olympic organizers have promised to deliver an equally inspirational ceremony.
| A．gone | B．to go | C．going | D．go |
We are so sorry for that．We'll try to determine exactly _________ went wrong that evening．
| A．where | B．what | C．which | D．how |