第一节 完形填空（共10小题；每小题2分，满分20分）
阅读下面短文，掌握其大意，然后从21~30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 21 should be made even before the choice of a curriculum（课程）in high school. Actually, however, most people make several job during their working lives, 22 because of economic and industrial changes and partly to improve their position.
