How often one hears children wishing they were grown-up, 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.

Youth is a time when there are few tasks 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. In addition, life is always presenting new things to the children—things that have lost their interest 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 continually being told not to do things, or being punished for what he has done wrong.

When the 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.

People can experience happiness if they______.

A．always think of the past and regret it

B．value the present

C．are no longer young

D．become old and have much experience