When your parents advise you to 'get an education' in order to raise your income, they tell you only half the truth. What they really mean is to get just enough education to provide manpower for your society, but not so much that you prove an embarrassment to your society. Get a high school diploma, at least. Without that, you will be occupationally dead unless your name happens to be George Bernard Shaw or Thomas Alva Edison, and you can successfully dropout in grade school. Get a college degree, if possible. With a B. A. , you are on the launching pad. But now you have to start to put on the brakes (刹车器，闸). If you go for a master's degree, make sure it is an M. B. A. , and is famous law of diminishing returns begins to take effect. Do you know, for instance, that long-haul truck drivers earn more per year than full professors? Yes, the average 1977 salary for those truckers was $ 24000. While the full professors managed to earn just $ 23030. A Ph. D. is the highest degree you can get. Except for a few specialized fields such as physics or chemistry where the degree can quickly be turned to industrial or commercial purposes, if you pursue such a degree in any other field, you will face a dim future. There are more Ph. D. s unemployed or underemployed in this country than any other part of the world. If you become a doctor of philosophy in English or history or anthropology or political science or languages or-worst of all-in philosophy, you run the risk of becoming overeducated for our national demands. Not for our needs, mind you, but for our demands. Thousands of Ph. D. s are selling shoes, driving cars, waiting on table, and endlessly filling out applications month after month. They may also take a job in some high school or backwater college that pays much less than the janitor earns. You can equate the level of income with the level of education only so far. Far enough, that is, to make you useful to the gross national product, but not so far that nobody can turn much of a profit on you. According to the first paragraph, the real reason for people to receive education is that they ______. A．will earn s lot of money B．will lead a happy life C．will become more intelligent D．can meet the demands of society as a source of manpower