Examination practice detection is uncontrollable, and students can cheat themselves by cheating.
When students encounter something they don't understand, they can't ask the teacher for advice at the first time.
Hardware requirements, computer or mobile phone, internet speed and stereo are all the costs of online education.
The communication cost is too high, and the problems that can be solved face to face may take 1 minute, and it may take a long time to explain online.