What do summarizing mean ?

What does fi stand for in the fitt-vp principle of exercise prescription?

Active immunity refers to: a. the defenses people are born with. b. temporary immunity granted from another source. c. immunity gained through immunization and exposure to diseases. d. natural immunities that protect humans from other animal diseases

Health-related fitness components include cardiorespiratory endurance, flexibility, and muscular strength. agility balance body composition reaction time