I did the various examples and B is the correct answer. You can either create create a calculated field or you can add the same code in the condition tab of the Filter to tie the filtering to the parameter. Hence, the answer is B.

I think B is the correct answer because we created a parameter name choose regio. So we need to add it into a filter card

I think the selected answer, B is correct

No, answer C is wrong. Of course, you can add Region to filters card but the question was about the parameter Choose Region and how to use it as a filter to interact with a chart. If we just add Region to filters card it has nothing to do with parameter and we can use this filter without parameter at all. That is why answer C is not the case. So we already have a parameter. Next we need to create a calculated field with formula [Region] = [Choose Region]. After that we put calculated field to filters card and set it to True. After we click show parameter and use it as a filter. This is how it works. So the right answer is B.

https://kb.tableau.com/articles/howto/filtering-data-with-a-parameter?lang=fr-fr

c-Add region to the filters card