Air pollution is obviously one of the major _____ of city life.

You needn’t introduce him to me. I’ve met him on several _____.

（ ） we have all the materials ready, we should begin the new task at once.

Hardly （ ） how I passed the interview.

Realizing that he hadn’t enough money and _____ to borrow from his father, he decided to sell his watch.

She is very （ ） to his ugly appearance.

_____ forget the days when we lived in the countryside.

When I heard that my mother would come to see me this weekend, I （ ） for her to arrive.

The authorities wouldn’t （ ） us permission to fly all the way down to San Francisco.

Any student who_____his homework is unlikely to pass the examination.

It was not known （ ） he had said during the interview.

I cannot tell the_____difference between the twins.