How many volts of electricity can an electric eel emit（）

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．should be introduced, for it really works at the school where he once studied
B．should not be introduced, for it may cause disturbance
C．should be introduced though it may not work effectively
D．needn't be introduced as long as teachers don't smoke in front of children