—Oh, it’s you. I didn’t ______ you just now!—That’s because I have just had my hair cut and I’m wearing new glasses.
His parents were so poor that they couldn’t _______ to buy a computer for their only son .
Who did the teacher , as well as the monitor , _______ an article for the wall newspaper?
The question _______ we can get enough coal for the winter has not been cleared up yet .
Every possible means ________ to prevent the air pollution , but the sky is still not clear.
Some people thought ________ possible to live on out space in the future .