V-ing 变化规则： 1) 一般加 ing . 如: play----playing watch----watching 2) 以不发音的e 结尾,去e 加ing. 如: take----taking come---coming 3) 元+辅结尾,且是重读闭音节的单词,双写辅音字母+ing. 如:run----running swim----swimming