阅读下面短文，掌握其大意，然后从1~15各题所给的A、B、C和D项中，选出最佳选项，并在答题卡上将该项涂黑。
Most worthwhile careers require some kind of specialized training. Ideally, therefore, the choice of an __1__ should be made even before choice of a curriculum in high school. Actually, however, most people make several job choices during their working lives, __2__ because of economic and industrial changes and partly to improve their position. The "one perfect job" does not exist. Young people should __3__ enter into a broad flexible training program that will __4__ them for a field of work rather than for a single __5__ .
