Final answer:
The correct way to fill in the blank is with C - The Andes Mountains, as it follows the grammatical rules for capitalization of proper nouns.
Step-by-step explanation:
The correct answer to the question is C - The Andes Mountains. When writing about geographical features such as mountain ranges, the proper noun should be capitalized. This includes both the descriptor 'The' and the name 'Andes Mountains.' This is in line with grammatical rules for proper nouns, which dictate that specific places and landmarks are treated with capitalized initial letters.