doing。teach作为动词后面可以直接加宾语，比如说，I taught English in ShandDong Province.所以，如果在后面加动词做宾语的话就要着把动词变成名词，比如 Mr Smith, who teaches swimming in our school,is very handsome.这里面说的教游泳，游泳是动词，所以要写成V...ing.