选泵时应考虑到泵的()压头和输送液体的性质。
A、流速
B、流量
C、流体
D、流动
参考答案:B
Mary, stop to have a rest. You _________ the flowers in your garden for nearly two hours.
A.are watering
B.were watering
C.water
D.have been watering
下列不属于非离子型表面活性剂的是()
A.司盘类
B.吐温类
C.卖泽类
D.苄泽类
E.硫酸化物