The washing machine was broken, but it is OK now.
It is repaired.
It has been repaired.
Please explain the correct choice. Is it possible that both are correct here?
"Repaired" really just refers to the process the washing machine underwent, not its present state.
"The washing machine is under repair", or "the washing machine is being repaired" would describe its state while the repair was underway.
Once the repair is over, the washing machine has been repaired.
The machine is now in a working state, so the washing machine is working.