Formal diction uses sophisticated language, longer and more complex words, and proper grammar, conveying a sense of complexity and deeper nuances. The correct answer here is C. A is incorrect because it uses slang or trendy words. B is incorrect because it does not use complex words. D gets closer to a more formal approach but does not evoke the deeper nuances of his thought pattern. C is correct because the use of the words pride, appearance, and strong, give a more complex and sophisticated picture of his attitude regarding his appearance, and giving the reader a deeper perspective of the subject.