David, could you tell me _________– Every four years.

There was no sign _______ they had died from diseases such as bird flu – the main worry in such cases. Among the theories was _______ a truck had collided（碰撞）with the crowd.

those troublesome messages, you’d better not give out your number to anyone whom you don’t know.

Susan didn’t like popular music very much, didshe— ___________now.

Although this medicine can cure youyour illness, it has a bad effect____you