The correct answer is D. The teacher told Harrison that he needed to find a new topic, do better research, and start citing sources correctly.
Step-by-step explanation:
A parallel structure is the repetition of a grammatical pattern or structure in a sentence, this usually means a list of element relates in the same way to other elements in a sentence which creates a parallel or equal relationship that shows all the elements have the same level of importance as these are introduced using the same grammatical structure. In the case of the sentence "The teacher told Harrison that he needed to find a new topic, do better research, and start citing sources correctly" the elements of the list are "to find a new topic, do better research, and start citing sources correctly" and each of them has a different grammar structure as the first one uses an infinitive "to find", the second one introduces the verb directly "do" and the third one uses two verbs "start citing" this means there is no repetition of grammar structures in the sentence and therefore there is not a parallel structure in this sentence. Thus, sentence D is the sentence that does not use a parallel structure correctly as each element is introduced using a different grammatical structure which is the opposite to parallel structures.