Respuesta :
C. You are not allowed on the dance floor unless you are a dancer, the choreographer, or you take photographs.
The sentence which has a mistake in parallel structura is option C. "You are not allowed on the dance floor unless you are a dancer, the choreographer, or you take photographs."
Parallel structure (also called parallelism) refers to the repetition of a chosen grammatical form within a sentence. By making each compared item or idea in your sentence follow the same grammatical pattern, you create a parallel construction.