1.They used closed-circut television.That's how they spotted the shop-lifter
if they had used closed-circut television , they would have spotted the shop-lifter
2.They asked him to leave the dining-room because he wasn't wearing a shirt
if he had worn a shirt , they wouldn't have asked  him to leave the dining-room
3.It took us a long time to find his house because the streets were not clearly marked
if  the streets had been clearly marked , it wouldn't have taken  us a long time to find his house
4.We didn't go by air only because we hadn't enough money
if we had had enough money , we would have gone by air only
5.The bus didn't stop because you didn't put your hand up
if you had put your hand up , the bus would have stopped