Answer:
Options C and D
C. You are not allowed on the dance floor unless you are a dancer, the choreographer, or you take photographs.
D. The reasons for why I need a new pair of shoes are manifold: they leak, they have stains, and they are too small.
Explanation:
Options C and D are the sentences that contain errors in parallel structure.
In option C, we discover that the words that follow "dancer" didn't follow the rule of a parallel structure. We have it there as "...a dancer, the choreographer, or you take photographs" - this is where the error lies.
The sentence didn't follow the same grammatical structure.
In Option D also, the error is found in "...they leak, they have stains, and they are too small". The grammatical structure isn't correct.
Parallel structure (also known as parallelism) is known to be the repetition of a chosen grammatical form. This repetition is done within a sentence. The use of parallel structure helps reading and also helps to make text easier to process.
