Question :
Last night, while they (sleep), a burglar broke into their house.
Answer A :
Last night, while they slept, a burglar broke into their house.
Or
Answer B :
Last night, while they was sleeping, a burglar broke into their house.
I want to tell someone about last night. I want to know whether it is correct or not to talk about the past used with while grammar. Past simple or past continuous, which is more appropriate to combine with while?