对电梯的舒适感，常以（）作为主要性能指标。①速度特性②工作噪音③平层准确度④速度高低
A.②③④
B.①③④
C.①②③
D.①②③④
参考答案：C
被称为“乐府双璧”的是《木兰诗》和哪一首民歌？
His salary as a driver is much higher than（）.
A.a porter
B.is a porter
C.that of a porter
D.as a porter
