单选题 Helen groups all people into two ______: those she likes and those she dislikes.
【正确答案】 C
【答案解析】解析：category n．类，种类，类别。hierarchy n．(社会的)等级制度，等级森严的组织；统治集团，领导层。catalogue n．目录(册)。species n．(单复数不变)(生物的)种，物种。