Scientists and experts said it was a big ________in China's space history that Chang'e-II has been smoothly sent around the moon.
| A．leap |
| B．chance |
| C．time |
| D．opportunity |
One ought __________ for what one hasn’t done.
| A．not to be punished | B．to not be punished |
| C．to not punish | D．not be punished |
Luckily good things _________ here to save local wildlife.
| A．are doing | B．are being done |
| C．had been done | D．will do |
The earth became so violent that it was not clear_________ the shape would last or not.
| A．if | B．how | C．whether | D．why |
__________ she couldn’t understand was _________ fewer and fewer students showed interest in her lessons.
| A．What; why | B．That; what | C．What; because | D．Why; that |
The clever boy made a hole in the wall, ________ he could see what was going on inside the building.
| A．on which | B．at which | C．through which | D．in which |