It is difficult ____the students ____get to school in Yunnan.
| A．for,for | B．to,for | C．for ,to | D．to,to |
Each of the girls________wearing a beautiful skirt now．
| A．is |
| B．are |
| C．am |
| D．be |
Please tell us how things used________．
| A．to be |
| B．being |
| C．to being |
| D．be |
They volunteer________at the local hospital．
| A．to work |
| B．working |
| C．work |
| D．to working |
That boy looks very unhappy．Let’s________．
| A．to cheer up him |
| B．to cheer him up |
| C．cheer him up |
| D．cheer up him |
His sister usually helps him________his homework．
| A．doing |
| B．do |
| C．does |
| D．to doing |