题目

阅读短文，从每题所给的A、B、C、D四个选项中，选出能填入空白处的最佳选项。 People in the US have been encouraged for decadesto eat various kinds of food, as the variety of food helps to 1 thatthey keep a 2with enough nutrition. But this week a groupof nutrition experts said that longstanding 3might be out of date. The advice to 4 different kinds of food has been included in thegovernment's Dietary Guidelines for Americans《美国居民膳食指南》for quite some time.It.is 5 based on 6 studies of low-income populations. The studiesclaimed that consuming vario 下列句子没有语病的一项是（         ） A．二十一世纪需要有科学文化的一大批知识分子去建设祖国。 B．在学习实践中，我们要善于运用科学的学习方法。 C．是否具有良好的心理素质，是考试取得好成绩的条件之一。 D．经过大家的共同努力，使我们完成了制作怀旧网页的工作。