Which is the topic sentence of the following paragraph?

on the day of my piano recital, i was experiencing nervousness. i felt as if grasshoppers were jumping on my skin. although i had been practicing the waltz i was going to play, i was afraid the worst would happen. as the day wore on, i grew increasingly fearful. i couldn’t concentrate on anything until the moment of my performance finally arrived.
question options:

a) as the day wore on, i grew increasingly fearful.

b) although i had been practicing the waltz i was going to play, i was afraid the worst would happen.

c) on the day of my piano recital, i was experiencing nervousness.

d) as the day wore on, i grew increasingly fearful. i couldn’t concentrate on anything until the moment of my performance finally arrived.