分馏塔液面波动的原因有（）。
A、塔压波动
B、进料量波动
C、液控阀失灵
D、塔底泵抽空
参考答案：A, B, C, D
用科学记数法表示0.00608的结果是 [ ]
A.6.08×10-3
B.6.08×10-4
C.0.608×10-3
D.0.608×10-2
________ you didn't know the rules won't be an excuse for your failure to report.
A．That
B．Where
C．What
D．Why
