1.He can't play football because he hurt his shoulder.
2.I can't open the door because i lost the key.
3.I know this story very well because I read the book.
4.I can't send the letter because I don't have an envelope.
5.He can't go to the gym because he ate too much.
6.They can't buy a new flat because they didn't save money.
7.We know Mary because we met her at the party last Saturday.
8.We don't know how old is jim because we don't know him well.
9.John won't take a cigarette because he gave up smoking.
