have to~must
L17：Jennifer will have to take part in a new play soon.
L39：The doctor told him that he would have to stay in hospital for another two weeks.
L50：You'll have to get off here.
L52：I actually have to walk on them to get in or out of the room.
L65：It was fortunate that we didn't have to carry him.
L84：Before they drive any of the buses, they will have to pass a special test.
L90：Oil rigs have to be repaired frequently.
L90：Divers, who often have to work in darkness a hundred feet under water, have been frightened out of their wits by giant fish bumping into them as they work.
ought to~should
L65：A policeman approached Jimmy and told him he ought to have gone along a side street as Jumbo was holding up the traffic.
used to~would
L31：Before he retired, Frank was the head of a very large business company, but as a boy he used to work in a small shop.
L31：In his twenties Frank used to make spare parts for aeroplanes.
L35：RoyTrenton used to drive a taxi.
L55：The machine was used in a cave near the seashore where -- it is said --pirates used to hide gold.
L59：Our dog,Rex, used to sit outside our front gate and dark.
L79：I used to travel by air a great deal when I was a boy.
L79：My parents used to live in South America and I used to fly there from Europein the holidays.
be able to~can/could
L28：Because of this, he has not been able to get his own car into his garage even once.
L33：Nearly aweek passed before the girl was able to explain what had happened to her.
L43：Though, at first, Byrd and his men were able to take a great many photographs of the mountains that lay below, they soon ran into serious trouble.
L43：The plane was then able to rise and it cleared the mountains by 400 feet.
L43：Byrd now knew that he would be able to reach the South Pole which was 300 miles away, for there were no more mountains in sight.
L43：The aircraft was able to fly over the endless white plains without difficulty.
L48：When the dentist at last removed the cotton wool from my mouth, I was able to tell him that he had pulled out the wrong tooth.
L53：Yesterday the firemen examined the ground carefully, but were not able to find any broken glass.
L53：In this way, he was able to solve the mystery.
L67：Tazieff was able to set up his camp very close to the volcano while it was erupting violently.
L67：He waited until the volcano became quiet and he was able to return two days later.
L67：He has been able to tell us more about active volcanoes than anyman alive.
L79：Fortunately, nothing was found and five hours later we were able to take off again.
L91：He informed the station at once, but no one there was able to explain the mystery.
L95：If I had been, I would not have been able to get home for lunch.
