There are five pairs _______, but I'm at a loss which to buy.
| A．to be chosen | B．to choose from | C．tochoose | D．for choosing |
our earth, or else it will be no longer fit for us to live on.
| A．Protected | B．To protect |
| C．Protecting | D．Protect |
With temperature ______ so rapidly, we could not go with the experiment.
| A．fall | B．falling |
| C．fallen | D．to fall |
They've won their last three matches, I find a bit surprising.
| A．which | B．that | C．when | D．what |
It's 5 days we came here. Why shouldn't we start?
| A．when | B．before | C．as | D．since |
in the fields on a March afternoon, he could feel the warmth of spring.
| A．To walk | B．Walking |
| C．Walked | D．Walk |