.

---How long are you going to stay in the country?

--- It’s hard to say. ______.

A．I don’t want to go there

B．It all depends

C．It doesn’t matter

D．That’s nothing

继电保护按故障判据分类有过流、低压、低周、零压、失磁、零流，另外非电量：温度、瓦斯保护。