By the middle of the 21st century , the vast majority of the world’s population ________ in cities rather than in the country.
He tried to invite some famous pop stars to sing in the concert ______, but failed.
_____ we have finished the course, we shall start doing more revision work.
I don’t like the way ________ Mr. Wang treats his children.
I meant to help him . ______, he didn’t accept my offer.
Several months later, he found his deskmate very difficult _______.