The correct option is (D): utrvuv
Explanation: To find the missing letters in the sequence "rst-vrs-uv-stu-rst," we need to identify a pattern. The sequence shows a gradual shift, where each segment transitions to the next by modifying the letters. The option "utrvuv" fits best as it continues the pattern of transformation seen in the previous segments, maintaining the sequence's flow. Therefore, the correct answer is Option D – "utrvuv."