“you -borrow my notes provided you take care of them "i told

“you _borrow my notes provided you take care of them "i told my friend.
1,could 2,should 3,must 4,can
选4.考察的知识点是什么?
确定选4.我和三楼有一样的疑惑，什么时候用COULD ,什么时候用CAN...