单项选择题
A.more beneficial it will be to science B.more powerful will be its electrical charge C.easier it will be to find D.tougher it will be to eat
A.To warn the reader to stay away from them. B.To compare their voltage to that used in houses. C.To give an example of a living electrical generator. D.To describe a new source of electrical power.
A.1,000. B.800. C.200. D.120.