Scientists say it may be five or six years （ ） this medicine is tested on human beings.

Little （ ） to win your friendship in this way.

No one should blind himself （ ） the well-known fact.

To save energy, people have to （ ） their electricity consumption.

Such a skilled tennis player knows how to take_____of his opponent’s (对手) chief weakness.

Herman’s success is （ ） his hard work and his academic ability.

The sales manager had his secretary _____ a press conference for their new products.

Many students thought about the third question for quite a while and had great difficulty answering it. Obviously， it was _____ all.

_____ the members cooperate well, the team will keep winning games.

Kim went to visit the teachers in the primary school ______ he worked three years ago.

She heard a terrible noise, （ ） brought her heart into her mouth.

It was only by a great effort of will and courage that he was able to （ ） himself together.