Final answer:
The most formal phrase is 'His pride in his appearance was strong'.
Step-by-step explanation:
The phrase that uses the most formal diction is C. His pride in his appearance was strong. This phrase employs more formal language by using complete sentences and replacing contractions ('wasn't' becomes 'was not') and abbreviations ('w8s' becomes 'was'). Additionally, the phrase conveys a sense of strong emotion and emphasizes the value placed on personal appearance, which is often associated with formal language usage.
Learn more about Formality in diction