酸洗废酸从1号酸罐通过废酸泵排至酸再生，新酸从酸再生通过酸泵供至（）号酸罐。
参考答案：3
如图所示，金属板A、金属网B、荧光屏C彼此平行，A、B之间的距离d1=9cm，
B、C之间的距离d2=18cm，电源电动势E=20V，内阻r=2Ω，滑动变阻器在0～18之间可调，图中滑动片置于电阻的中点，从S孔向各个方向以速度V0=1×105m/s向电场中射入电子，电子的比荷qm=1.8×1011C/kg，不计电子重力．
求（1）A、B之间的电场强度E
（2）设所有电子都能打在荧光屏上，求屏上亮圆的半径．
When assessing a client as a candidate for crutch walking, the nurse should take into account that for some elderly people, crutch walking is an impractical goal primarily because which of the following reason
A．Decreased reaction time.
B．Decreased visual acuity.
C．Decreased motor coordination.
D．Decreased level of comprehension.
