"Làm ơn lặp lại!"
Not really related but, most of the language in this course can be considered disrespectful. It seems like you guys have made this course with the idea of having an audience that uses this course to use it and visit Vietnam as a tourist. It's nice and all but 'tôi' can be considered disrespectful to some people. You should have a course where it teaches to speak respectfully. Example: if youre talking to an older male, anh, ong, chu etc. or older woman, chi, co, ba. And most of this is in Mien Bac dialect (i think) I just know its not Mien nam dialect. Thanks.
I answered "please repeat that" and it was given as being wrong. Semantically there is no significant difference between "please repeat" and "please repeat that" in English. Moreover "please repeat", in most contexts, would sound extremely abrupt when said by an English speaker. At least it does to me.