✅ In option D, "Committee" is correctly capitalized because it refers to a specific, unique, and often formally recognized body within a given context, functioning as its de facto proper name (e.g., "The Steering Committee," or simply "The Committee" when everyone knows which particular committee is meant). This capitalization is crucial as it distinguishes this specific, named entity from "a committee," which would be a common noun referring to any general group formed for a purpose.

❌ Option A is incorrect because "Soldier" and "Country" are generally common nouns and should not be capitalized in this general context. Capitalizing them suggests they are proper nouns, which they are not here.

❌ Option B contains two proper nouns: "Vatican City" (a specific geographical and political entity) and "Pope" (a specific title for a unique individual). While "Pope" is correctly capitalized, it inherently functions as a proper noun when referring to the head of the Catholic Church; it does not "often appear as a common noun" in the same way "committee" does, where capitalization critically distinguishes a specific entity from a general one.

❌ Option C is incorrect. While "Medicine" as an academic discipline can be capitalized (making it a proper noun), "Graduation" is generally a common noun referring to the event. It is only capitalized if it's part of a specific named event (e.g., "Spring Commencement Graduation"); in this general usage, it should be "graduation."