The best choice to add to the passage in order to keep the perspective consistent is:
A. Dmitri had tumbled backward into a giant potted plant. I sighed and shook my head. There wasn't enough money in the world to make babysitting the Karamazov ninjas worthwhile.
This option maintains the first-person perspective of the babysitter and aligns with the tone and style of the original passage, effectively conveying her exasperation with the situation.