53,it's very cold so we can't go swimming

->IF IT WEREN'T VERY COLD . WE COULD GO SWIMMING

54,His friends were so late, so they missed the train
-> If his friends hadn't been so late, they'd not have missed the train.
55,She said " If you feel faint,you should sit down and put your head between your knees".
->She advised me to sit down and put my head between my knees if I felt faint.56,
56," If you don't pay the ransom,we'll kill the boy", said the kidnappers.
->The kidnappers said that if I didn't pay the ransom, they would kill the boy.
58," I have missed the train. Now I will be late for work and my boss will be furious",said Bill.
->Bill said that he had missed the train, then he would be late for work and his boss would be furious.
59,''We'll wait for you if you're late'', they said.
->They said they would wait for me if I was late.