I believe the answer is A, I had this same question on a test last year, and I'm pretty sure that's the answer.
The reason why this can happen is because of the transformative journey that Jin Wang is on. At first, Jin Wang is ashamed of being Chinese, and wants to appear as white as possible. Wei-Chen is fully Chinese, and because of this, he is a foil, as he is a character that highlights the characteristics of the protagonist by contrasting them with his own, which are the opposite.
However, as the story progresses, Jin Wang becomes even less similar to Wei-Chen, as he kisses Suzy and as he transforms into Danny. Jin Wang, therefore, not only contrasts with Wei-Chen, but is in open opposition to him. This makes Wei-Chen the antagonist.
I think the answer is B. It is not A, for it IS mandatory as it says that in the text. It is not C, because it is not said in the text, and it is an opinion. And it is not D, yet it is true. It has not been spoken of in the text. Therefore, B is your best bet. Hope this helps!
