Final answer:
The appropriate expression to fill in the blank is 'Qué rollo' which conveys the speaker's dislike and disinterest in the subject of mathematics.
Step-by-step explanation:
The appropriate expression to fill in the blank in the sentence 'No me gusta la clase de matemáticas' is B. Qué rollo. This expression translates to 'What a drag' or 'How boring' in English. It conveys the speaker's dislike and disinterest in the subject of mathematics.
Learn more about Expression of dislike for a school subject