I feel like "must not" is closer to "không nên"- saying must not suggests there's still a possiblity and "không được" is more like he can't.
Can vào be omitted?
Wouldn't Đứa trẻ không được đi bơi vào ngày mai be the child can't go swimming tomorrow?
I left out "vào" and was marked correct. So good question?
Is it possible to use 'phải' instead of 'được' here? How would we structure that sentence? I tried 'Đứa trẻ phải không đi bơi vào ngày mai' but it was marked incorrect.