Be sure to buy real questions and test guides. You can also buy a book when you have time to read. The rest depends on your personal needs. Online course is the whole process of adult undergraduate English customs clearance. If I remember correctly, this course seems to be a course of scanning QR code in NPC books. The disadvantage of this course is that it is not convenient for the teacher to read the secretary's notes on the blackboard occasionally, so it depends on personal choice.