---Why did Tom become wealthy this year?---Because he sold _________________ he did last year.
Along with the letter was his promise ________he would visit me this coming Christmas.
I was just talking to Margaret when Jackson________.
Now many crops can be improved ________different species of plant, such as rice, wheat.
________of food ________to the countries struck by the seaquake(海啸).
Each player of chess is trying to trap the other player's king into a position ________escape is impossible.