Answer:
Letter D is correct.
Explanation:
According to Cambridge Dictionary, paraphrasing means to "repeat something written or spoken using different words." The intention of this exercise is to make the words shorter and simpler, so the reader can understand with his or her own words what the speaker wanted to say.
It is not necessary to break the original text into individual sentences; even though it can help at the beginning, isolating sentences can create more problems that the ones can solve, specially because it may make the reader understand each excerpt as an individual one.
Even if you are paraphrasing, it is necessary to credit the source to indicate the words that are being paraphrased.
Letter C is also incorrect because it is not mandatory to substitute phrases <em>here and there</em> (it is not a must), specially if there are phrases from the text that can help readers understand it as written.
Letter D is correct since paraphrasing respects the main idea of the original passage, even the words could be changed to some closer to the reader's speech, so he can understand the passage.