电解质水平低的危害有（）。
A.炭渣分离不良
B.电流效率下降
C.引起突发效应
D.导电率下降
参考答案：A, B, C, D
The city of Qingdao has been working on building itself up as a city of sails ________ it successfully hosted the 2008 Olympics’ sailing program.
A．after
B．since
C．when
D．until
