"Đó là một sự lựa chọn đúng."

Translation: That is a correct choice.

[LostinVN]

This sounds weird in English. If it's the right one and it is a choice then we can assume there is only one right choice. Therefore we say: that is the right choice NOT that is a right choice.
Can you give me an example of when to would have more than one correct choice?

[wordgeek416]

How about a multiple-choice test where more than one choice may be correct?

[Johnathan363023]

Agreed, it should be the correct choice.