Once______ a difficult and even dangerous place______，Vietnam is now a friendly destination that welcomes visitors from all over the world.
| A．considered; visiting | B．considered; to visit |
| C．considering; visiting | D．considering; to visit |
—Could you tell Lily the meeting place?
—Sure, I will __________ when I see her.
| A．immediately | B．probably | C．certainly | D．merely |
Tom tried to __________ in German.
| A．understand himself | B．make himself understanding |
| C．make himself understood | D．make himself understand |
I wonder how many years ago ___________.
| A．did your father retire | B．has your father retired |
| C．your father retired | D．your father has retired |
He said that he would write to us but so far we ___________ from him.
| A．didn’t hear | B．haven’t heard | C．shouldn’t have heard | D．hadn’t heard |
__________ good exercise.
| A．Climbing hills is | B．Climbing the hill is |
| C．The climbing hills are | D．The climbing of hills are |