51.  at least you mustn't change your mind at your pleasure if something unexpected really prevents you from coming, you must tell the host or hostess about it several days before the dinner for at that time the host or hostess must have begun to go shopping and prepare for the dinner it is always considered impolite to tell the host or hostess that you are not able to came at the last minute .

52.  "set's get into the boat and go before they come back again."

53.  In this several weeks , several new teachers came to our school and practised to each us.

54.  The students who came from training college taught for several weeks.

55.  Though the students who came from training college will leave, I hope we can see their shadow in our school in the future.

56.  That meaned the autumn was coming.

57.  This invention of his will greatly benefit the whole world, so two government officials would come for the papers at eleven o'clock in the morning.

58.  Shortly after that, two police officers came to his house.

59.  The end of term is coming, we shouldn't waste time to do the others things.

60.  The final exam is coming.