A、A child has to go to school. B、A child doesn’t have enough money. C、A child is restricted to doing something he wants to do. D

How often one hears children wishing they were grown-ups, and, old people wishing they were young again? Each age has its pleasures and its pains, and the happiest person is the one who enjoys what each age gives him without wasting his time in useless regrets.
    Childhood is a time when there are few responsibilities to make life difficult. If a child has good parents, he is fed, looked after and loved, whatever he may do. It is impossible that he will ever again in his life be given so much without having to do anything in return. What’ s more, life is always giving new things to the child—things that have lost their in terest for older people because they are too well known. But a child has his pains: he is not so free to do what he wishes to do; he is repeatedly being told not to do something, or being punished for what he has wrongly done.
    When a young man starts to earn his own living, he can no longer expect others to pay for his food, his clothes, and his room, but has to work if he wants to live comfortably. If he spends most of his time playing about in the way that he used to as a child, he will go hungry. And if he breaks the laws of society as he used to break the laws of his parents, he may go to prison. If, however, he works hard, keeps out of trouble and has good health, he can have the great happiness of building up for himself his own position in society.
Questions 19 to 21 are based on the passage you have just heard.
19. What should people do to be the happiest person?
20. What is the disadvantage of being a child?
21. Which of the following statement is NOT true according to the passage?