【正确答案】:
A STEM CAN BE DEFINED AS A FORM TO WHICH AFFIXES OF ANY KIND CAN BE ADDED. "NATION, NATIONAL, INTERNATIONAL, INTERNATIONALIST" ARE ALL STEMS.
【题目解析】:词干可以定义为可以添加任何词缀的形式。“nation(国家), national(国家的), international(国际的), internationalist(国际主义者)”都是词干。