When their battery is low, they can charge themselves.
举一反三
- When the car is at low speed, coasting or idling, only the battery offers the electric power to the motor．
- When the engine, generator and battery work together to supply right amount of electric power to the electric motor, or the engine and the generator charge the battery pack, it operates in series mode．
- Very low fertility can become ______ , and children of one-child families want usually only one child themselves.
- When the investor views the user of funds as a low risk borrower, he/she will charge the user a risk premium.()
- Who will most probably take care of the middle-aged Americans when they need care themselves（） A: They themselves. B: Their close friends. C: Their children. D: Their husbands or wives