____ the police know the killer's identity, they are getting close to catching him.
A dictionary is a book ______ gives the meanings of words.
The old town has narrow streets and small houses ________ are built close to each other.
Do you want a friend ______ you could tell everything to?
—May I see your ticket, please? I think you ________ in my seat.—Oh, sorry. My seat is upstairs.
The teacher told the kids that light ________ faster than sound.