单选题 Attendants on the train treated all the passengers ______ and made sure they were comfortable during the trip.
【正确答案】 C
【答案解析】[解析] 副词位置
空格处需要填入一个副词来修饰动词treated，所以副词C. courteously(有礼貌地)是正确答案。过去分词和动词A，形容词B，现在分词和动名词D都不能修饰动词。