由幂函数y=$x^{\frac{1}{2}}$和幂函数y=x³图象围成的封闭图形面积为（　　）

根据短文内容，选择正确答案。

    Peter was a small boy. He lived with his parents in a small house near some hills. The people there were all poor.

    One night it was very dry and windy. When everybody was asleep, Peter suddenly heard some noise. It came out from the kitchen. He got up and walked to the kitchen. He found that the wood beside the stove was burning. There was no water tap (水龙头) in the house, so he could not put out the fire. He shouted loudly to wake up everyone in the house. Then he ran out of his house and knocked on the doors of many houses to wake the people up. They all left their houses quickly.

    At last the firemen put out the fire. Many people lost their homes. But luckily, all of them escaped the fire with a whole skin.

下列句子中加下划线词语使用不正确的一项是（    ）