I didn't know the way to the railway,so I asked a ____ for help

I didn't know the way to the railway,so I asked a ____ for help

I didn't know the way to the railway station,so I asked a __policeman__ for help.
我不知道去火车站怎么走,所以我问了一个警察.
policeman 警察

police
我不知道去火车站的路,所以我让一个警察帮忙