I believe the answer is c
Answer:
Narrator, his cousin, Lou, and the Painter Lady. The two children want to stop the Painter Lady from taking over "their wall."
Explanation:
The answer is D, it is diverse with international themes etc...
Your answer should be WHO.
Think of it like this: You wouldn't say "The boy it (a variant of 'which')", because it simply just sounds odd. Instead, you're wired to think "The boy, he (an unknown name, so it would be 'who')".