Which sentence is written incorrectly?

A) The two students who started a fight at the pep rally, both sophomores, were removed from the gymnasium.

B) The committee looked at two solutions for the sudden drop in tax revenue- - both of which, were valid.

C) Although I'm not usually scared of dogs, I have to admit that seeing a Great Dane without a leash in my yard made me pause.

D) Sophie wanted to show off both her new instamatic camera and her brand-new, super-expensive, purple shoes.