PLEASE HELP! Which sentence represents an example of exposition in a character-driven story?

a.) I wished I could flip the clock back half a minute to the time before I knew.
b.) Alex, as the whole world knew, was my best friend and was not a member of the team.
c.) I could smell Kate's strawberry shampoo and the hint of chlorine that clung to our clothes and bags.
d.) I didn't make a peep; instead, I leaned in closer, straining my ears like crazy to hear what the scandalous secret was.