Now the question that you must carefully consider is _____ can be put into practice.
| A．how what you have learned | B．how you have learned |
| C．that why you have learned | D．how that you have learned |
Earth is believed ______ by an object the size of Mars at some point in the distant past before itssurface cooled.
| A．to be hit | B．to have hit |
| C．to have been hit | D．to hit |
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 |