One of the teachers rewards is that he is using his mind on valuable subjects. All over th

e world people are spending their lives either on doing jobs where the mind must be kept numb(麻木的)all day, or else on highly rewarded activities which are tedious. One can get accustomed to operating an adding-machine for five and a half days a week, or to writing advertisements to persuade the public that one brand of cigarettes is better than another. Yet no one would do either of these things for its own sake. Only the money makes them tolerable. But if you really understand an important and interesting subject, like the structure of the human body or the history of the two World Wars, it is a genuine happiness to explain them to others, to welcome every new book on them, and to learn as you teach. With this another reward of teaching is very closely linked. That is the happiness of making something. When the pupils come to you, their minds are only half-formed, full of black spaces and vague notions and over simplifications. You do not merely insert a lot of facts, if you teach them properly. It is not like injecting 500 C. C. of serum(血浆), or giving a years dose of vitamins. You take the living mind, and mould it. It resists sometimes. It may lie passive and apparently refuse to accept anything you print on it. Sometimes it takes the mould too easily, and then seems to melt again and become featureless. But often it comes into firmer shape as you work, and gives you the incomparable happiness of helping to create a human being. To teach a boy the difference between truth and lie in print, to start him thinking about the meaning of poetry or patriotism, to hear him hammering back at you with the facts and arguments you have helped him to find, sharpened by himself and fitted to his own powers, gives the sort of satisfaction that an artist has when he makes a picture out of black canvas and chemical colorings, or a doctor when he hears a sick pulse pick up and carry the energies of new life under his hands.

What makes people tolerant of tedious jobs is______.

A．the job itself

B．the money

C．the significance of the job

D．the fact that it can keep the mind numb