A permanent magnet assists closing and latches the breaker in the closed position .in the above sentence,the "permanent magnet"means" 永久磁铁".
A.1
正确答案是A
A permanent magnet assists closing and latches the breaker in the closed position .in the above sentence,the "permanent magnet"means" 永久磁铁".
A.1
正确答案是A