Which of the following best explains how interacting central ideas differ from a single central idea?

Which of the following best explains how interacting central ideas differ from a single central idea?
a.
Interacting central ideas connect causally so that one condition produces another, building a more layered social argument
b.
A single central idea is stated directly, while interacting central ideas emerge through dialogue
c.
A single central idea develops through plot events, while interacting central ideas develop through setting details
d.
Interacting central ideas require multiple protagonists, while a single central idea follows one character