题目

The famous movie star didn't refuse ______ the poor children．A. help B. helpsC. to help D. helping 答案：【答案】C【解析】句意：这位著名的电影明星没有拒绝帮助贫困儿童。A. help动词原形；B. helps第三人称单数形式；C. to help 动词不定式；D. helping动名词或现在分词。根据固定用法refuse to do sth. 拒绝做某事。可知，此空应填to help，故选C。给出下列命题：①若a＞b，则1a＜1b；②若a＞b，且k∈N*，则ak＞bk；③若ac2＞bc2，则a＞b；④若c＞a＞b＞0，则ac-a＞bc-a．其中假命题是 （只需填序号）．