The importance of saving gas________be stressed too much.Automobiles use up some 70 billion gallons of gas a year.[ ]

下列各句中，表达得体的一句是

23. Each member country of WTO must ______ its laws and regulations and compete on the principle of fairness and co-operation.

When he looked up, he suddenly found himself_____ by a group of teenagers,_____ looked at him anxiously[ ]

Though the road success is hard, you will it.