动词+ing 形式可用于动名词和现在分词两种形式。现在分词为作为动词词性+ing 后所得，动名词为动词后+ing 后变为名词词性。扩展知识只能是动名词的情况作主语——主语只能是一个名词性的概念，动词不定式，主语从句都可以做主语例：Eating too much is bad for your health.特别说明：动名词作主语谓语动词是单数!作表语，可转换成主语例：Her favorite sport is skating. =Skating is her favorite sport.特别说明：不定式和动名词均可用作主语和表语有区别区别是：动名词多指笼统的、抽象的概念，而不定式则多指具体的、一次性的动作。作宾语，放在动词或介词之后例：She likes singing and dancing.Thank you for helping us.
