Board composition and term: limits directors, mandates reserved seats, five-year elected tenure, and limited non-voting co-option. The provision sets the board composition and limits elected directors to twenty-one, requires reservation of specified seats for Scheduled Castes or Scheduled Tribes and for women, fixes a five-year term for elected members and office bearers with conterminous tenure, allows nomination to fill casual vacancies under a timing condition, permits state-law co-option of up to two experienced non-voting specialists who cannot be office bearers, and excludes functional directors from the statutory maximum director count.