超声波流量计介质的（）不影响声波的传输速度。
A.介电特性
B.温度
C.压力
D.形态
参考答案：A
The reason ____ he was late for class was ____ he stayed up late last night.
A．why; that
B．why; because
C．that; that
D．that; because
某生活垃圾C、H、O、S、的元素组成分别为0.134kg/kg、0.017kg/kg、0.152kg/kg和0.001kg/kg，含水量在49.1%，则其干基发热量为（）。
A.8383kJ/kg
B.8429kJ/kg
C.1019kJ/kg
D.4267kJ/kg
