动词ing的变化规则：
1．一般情况直接＋ing
例:sweep-sweeping read-reading
2．以不发音e结尾的去e＋ing
例：take-taking make-making have-having
ride-riding
3．重读闭音节一个辅音字母结尾,双写辅音字母＋ing
例：shop-shopping sit-sitting swim-swimming,put-putting,begin-beginning
run-running ,cut-cutting 等