GMAT Sentence Correction (SC) | Re: Under high pressure and intense heat, graphite, the most

Options A, B and C can be eliminated on the same ground:
The use of conjunction "and" calls for another verb (to be parallel with "changes"): "changes and remains" is the correct parallel structure. Therefore options A, B and C can be eliminated because they use present participle "remaining", which cannot be parallel to the verb "changes".

Between options D and E, E is better due to concision
...

---