下列各句中，没有语病的一句是（ ）

She learned to playpiano all by herself.

Much to my surprise, the trapped girl _____ stay alive in the ruins for up to seven days with nothing to eat or drink.[ ]

What is your uncle —___________.

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