溶解氧的浓度随大气压的变化而不同，所以最好采用（）补偿。
A、零点
B、温度
C、大气压
D、添加试剂
参考答案：C
The reason ________ he explained was________ he was ill and unable to go to school.
A．why; that
B．why; because
C．which; because
D．which; that
电杆及拉线的埋地部分与通信（地区、站场）、信号直埋电缆的最小距离为（）m。
A.0.6
B.0.8
C.1.0
D.1.2
