Answer:
b) it is the general topic of the passage
Step-by-step explanation:
a) is incorrect because the central idea of a passage is often not specific, and instead more general, allowing for the writer to discuss sub-topics as well.
c) is incorrect because the central idea of a passage is an message/theme instead of a subject.
d) is also incorrect since the central idea is what the argument revolves around, not the evidence.
i hope this helps! :D