All four year colleges require high school students to complete number of years of english to be eligible for admission.

Four number of years of English.

Explanation:

English remains the most distinctive subject as this is the only subject that a student is required or recommended(sometimes) to study for four complete years in High School. During the admissions, the colleges expect one to possess strong reading and writing skills as these are the crucial elements for one's growth and career. However, different colleges have distinct eligibility criteria yet the four-year high school knowledge of the subject forms the core of all other criteria as an impressive academic school record is evidence of the potential performance in the college. They look for the candidates who could counter and cope-up with the upcoming challenges.

i would have to say "a" or "d".