1. My grandparents are good ___ me.
2. Swimming is good ___ us.
3. I am good ___ swimming.
4. It is good ___ him to lend you his eraser.
(Someone) is good to (someone).
(Doing something) is good for (someone).
(Someone) is good at (doing something).
It is + good + of + (someone) (to do something).
It is good of （人）（去做某事）
圖片來源： “Ace Minds: Prepositions” Book 3, published by Kidz Education