直流电阴极的变化为（）
A.神经肌肉兴奋性降低
B.细胞通透性增高
C.组织水分增多
D.产生碱性物质
E.细胞膜疏松
参考答案：B, C, D, E
在积雪覆盖的冰雪路行车时，可根据路边树木、电杆等参照物判断行驶路线。
The news came as no surprise to me. I ______ for some time that the factory was going to shut down.
A．knew
B．had known
C．have known
D．know
