Paul doesn't have to be made __________. He always works hard.
| A．learn | B．to learn |
| C．learned | D．learning |
—Where is he exactly?
—I don’t know, but I saw him _______ an experiment in the lab when I passed by.
| A．to conduct | B．conducted |
| C．conducting | D．conduct |
The tourism of my hometown _______ a rapid growth over the last decade. Now it’s the 2nd most visited place in our city.
| A．saw | B．had seen |
| C．is seeing | D．has seen |
To his mind, the collaborative development of Beijing, Tianjin and Hebei province is to solve the problems _____ Beijing faces, such as overpopulation, traffic jams, and etc.
| A．that | B．whether | C．when | D．why |
The houses for the low-income families _______ at present in our city will be completed next year.
| A．to be built | B．built |
| C．being built | D．having been built |
He spared no efforts to make himself _______ but failed.
| A．understand | B．understanding | C．understood | D．to understand |