Which of these phrases uses the most formal diction?
a. he was a snazzy dresser.
b. he cared about how he looked.
c. his pride in his appearance was strong.
d. he took time and care when getting dressed

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.