Titan is believed to be the only body in _____ solar system other than the Earth with liquid on ______ surface.
| A．the; / | B．/; the | C．/; / | D．the; the |
I was told that although these old buildings _______ the Qing Dynasty, they remained in good condition.
| A．are dated back to | B．dated back to |
| C．dating back to | D．have dated back to |
It was Alice and her friends who helped the homeless old woman,______?
| A．wasn’t it? | B．wasn’t she | C．didn’t they? | D．weren’t they? |
He felt _______ to remind the public to protect the environment.
| A．his duty | B．that is his duty | C．it his duty | D．it is his duty |
The research they had been devoted to ______ to be of great value to the cancer patients.
| A．is proved | B．proves | C．has proved | D．proved |
A week-long raining is coming, _________, the farmers say, will do harm to the growth of plants.
| A．it | B．that | C．what | D．which |