doing。teach作為動詞后面可以直接加賓語，比如說，I taught English in ShandDong Province.所以，如果在后面加動詞做賓語的話就要著把動詞變成名詞，比如 Mr Smith, who teaches swimming in our school,is very handsome.這里面說的教游泳，游泳是動詞，所以要寫成V...ing.