Read the sentence given below to find out if it contains any error. The error, if any, will be in one part of the sentence. If the sentence is error-free, select No error or option 5. Ignore errors of punctuation if any.

Dean wasn't sure whether it was her (A)/ natural aversion to anything (B)/ involving law enforcement (C)/ or concern to her boss' future (D)/. No error (E)