What capital letter is used to mark the word "repetition" for emphasis?

The capital letter used to mark the word "repetition" for emphasis is 'R.' When emphasizing a specific word such as "repetition," typically the first letter of that word is capitalized to draw attention to it. Capitalizing the first letter is a standard convention in English writing used for emphasis or to denote the importance of that term within a sentence or context.

The options provided include other letters, but they do not correspond to the word "repetition," as its emphasis is designated by the initial 'R.' Therefore, the correct emphasis lies in recognizing that capitalization is linked to the initial letter of the word in focus.