Answer:
gonna assume B
Explanation:
the others are about school stuff
Explanation:
their: meaning a person or their possession
there: meaning a place
they're: Meaning (they are) mixed together to meaning someone doing a action or describing someone.
I would say C probably. the text sort of explains how each decade is different from the previous one, but it doesn't seem to really show a strong "cause and effect."
sorry I wasn't very helpful.