Professor: What happens to gold when it is exposed to the air?
Student（after thinking it over）:It’s stolen.
John: Heat expands and cold contracts.（热胀冷缩） Teacher: You are right. Now, please give me an example. John：In summer, the days are long, and in winter the days are short.
Several weeks after a young man had been hired, he was called into the personnel director's office.
"What is the meaning of this?" the director asked. "When you applied for the job, you told us you had five years' experience. Now we discover this is the first job you ever held."
"Well," the young man said, "in your advertisement you said you wanted somebody with imagination."
Mike was late for school. He said to his teacher, Mr. Black, “Excuse me for my coming late, sir. I watched a football match in my dream."
"Why did it make you late?" inquired the teacher.
"Because neither team could win the game, so it lasted a long time." replied Mike.
Two attorneys（n.律师） went into a restaurant and ordered two drinks. Then they brought out sandwiches from their briefcases and started to eat. The owner marched over and told them, "You can't eat your own sandwiches here!"
The attorneys looked at each other, shrugged their shoulders and then exchanged sandwiches.
脑筋急转弯：
What is once in a minute, twice in a moment, and never in a thousand years?