The correct option is C.
The recommendation letter helps to complete the profile of an applicant. They provide information about how the student is from the perspective of someone who has worked closely with him during his high school career. The experiences that counselors and teachers have had of him can help paint a better overall picture of his accomplishments, potential and character.
Most selectives colleges and universities requiere one to three letters of recommendation with the application, usually, one from the vocational counselor and at least one teacher.