听力原文：Most worth-while careers require some kind of specialized training. Ideally, ther

听力原文： Most worth-while careers require some kind of specialized training. Ideally, therefore, the choice of an occupation should be made even before the choice of-a curriculum in high school. However, most people make several job choices during their working lives, partly because of economic and industrial changes and partly to improve their positions. The "one perfect job" does not exist. Young people should therefore enter into a broad flexible training program that will fit them for a field of work rather than for a single job.

Unfortunately many young people, knowing little about the occupational world or themselves, choose their lifework on a hit-or-miss basis. Some drift from job to job. Others stick to work in which they are unhappy and for which they are not fit.

One common mistake is choosing an occupation for its real or imagined prestige. Too many studentsor their parents choose the professional field, disregarding both the relatively small proportion of workers in the professions and the extremely high educational and personal requirements. The imagined or real prestige of a profession or a "white-collar" job is no good reason for choosing it as a life's work. Moreover, these occupations are not always well paid. Since a large proportion of jobs are in mechanical and manual work, the majority of young people should give serious consideration to these fields.

Before making a choice, a person should have a general idea of what he wants out of life and how hard he is willing to work for it. Each occupational choice has its demands as well as its rewards.

According to the passage, the economic and industrial changes as well as people's desire to improve their positions can usually lead to______.

A．the existence of "one perfect job"

B．the increase in t. raining programs

C．the changes in training programs

D．the decrease in the number of worth-while careers