分子筛再生峰值温度偏低的原因有（）。
A.吸附剂装填量偏低
B.分子筛再生气温度偏低
C.吸附剂使用周期长
D.再生质量差
参考答案：A, B, C, D
The murderer was brought in, with his hands ________ behind his back.[ ]
A. being tied
B. having tied
C. to be tied
D. tied
简述交换率的概念。
