A tourist will easily lose his way in Beijing ______ he has a map or a guide.
My mother often tells me ______ the teachers carefully
Look, Jim _______ football on the playground.
---Why did you laugh just now?---Ted wanted to tell us _____ very funny story, but he forgot ______ ending himself.
We should always be _________ the people who have helped us in our lives .
--- Mum,_ __ of the apples _____ gone bad.---- We'd better eat up the as soon as possible.