I found it quite necessary ______ a foreign language.
| A．learing | B．to learn | C．learn | D．to learning |
---So you've left the classroom key inside again?
---No.I've got it with me this time,but I have forgotten ______ the door?
| A．locking | B．locked | C．to lock | D．to have locked |
The number of smokers in the countryside is usually greater than _______ in cities.
| A．that | B．those | C．one | D．the one |
Most of us see a doctor ______ when we get a cold or something.This won't cost us a lot.
| A．suddenly | B．immediately | C．occasionally | D．frequently |
May I use your bike? I'm going to see my uncle who _______ this city.
| A．visits | B．will visit | C．has visited | D．is visiting |
It is playing computer games _______ the boy spends most of his spare time.
| A．that | B．which | C．when | D．how |