Final answer:
The correct sentence among the options is A, which properly capitalizes the names and has the correct use of uppercase and lowercase for common nouns and the beginning of the quotation.
Step-by-step explanation:
The correct sentence is A) 'When Ralph and Lauren went on a hike together, Ralph said, "Hey look at the boulder!"' This sentence is grammatically correct, with proper capitalization for the names Ralph and Lauren, the lowercase 'hike' as it is not a proper noun, and the capitalization of the first word after a quotation mark, 'Hey,' which is the start of a new sentence.