I asked my foreign teacher for leave and he replied to me. How should I answer this question?

God, why is your teacher angry with you? Do you still want to ask for leave? If you like, apologize and promise it won't happen again.

"I'm sorry, _ _ _ _ (professor's name), have to be leaving this time. I won't repeat this in the future. Thank you for your understanding. " I'm sorry I have to ask for leave this time. Not anymore. Thank you for your understanding. )

Yes, from personal experience, you can add "thank you for your understanding" at the end, and the other party will be speechless no matter how sad. Ha ha.