问题
单项选择题
Every means______tried but without any result．
A．have been
B．is to be
C．are to be
D．has been
答案
参考答案：D
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Every means______tried but without any result．
A．have been
B．is to be
C．are to be
D．has been
参考答案：D
一个原电池的总反应的离子方程式是Zn+Cu2+
Zn2++Cu，该反应的原电池组成正确的是
| A | B | C | D | |
| 正极 | Cu | Zn | Ag | Cu |
| 负极 | Zn | Cu | Cu | Zn |
| 电解质溶液 | CuSO4 | CuCl2 | H2SO4 | 酒精 |