be good at 擅长做...She is good at English.她擅长英语.
be good for..对...有好处.Vegetables are good for your health.蔬菜对健康有好处.
be good to do sth 做某事有好处.It's good to read books.读书是有好处的.
do well in 擅长.She does well in English.她擅长英语.跟第一个一样的意思.