Which Greek letter corresponds to the answer "K"?

Kappa is the Greek letter that corresponds to the answer "K". In the Greek alphabet, each letter has a specific equivalent in the English alphabet, and Kappa directly corresponds to the letter K. This makes it the correct choice when identifying which Greek letter represents K. In contrast, the other options refer to different Greek letters: Xi corresponds to X, Mu corresponds to M, and Phi corresponds to the letter P. Therefore, Kappa is the unique option in this case that aligns perfectly with the English letter K.