贫油含苯应控制在（）。
参考答案：≤0.4％
Jenny is on holiday now. I wonder ______________________.
A．when she will come back
B．when she came back
C．when will she come back
D．when did she come back
用硫酸再生阳床时采用分步再生法，再生液先以（）进行再生，然后逐步调整浓度、流速。
A.低浓度、高流速
B.低浓度、低流速
C.高浓度、高流速
D.高浓度、低流速
