题目

The palace caught fires three times in the last century, and little of the original building        now. A．remains          B．is remained         C．is remaining        D．has been remained 答案：A两台汽油机，甲的功率为乙的3倍，甲的效率为20%，乙的效率为25%，那么甲、乙每小时耗油量之比为    ．