How Does the Concept of Inclusive Fitness Explain Behavioural Traits

How does the concept of inclusive fitness explain behavioural traits like self-sacrifice (which clearly reduces the survival and reproductive opportunities of the individual who is self-sacrificing) ?

A) Inclusive fitness recognizes that the sum of an individual's behaviour includes both rational and irrational behaviour.
B) Inclusive fitness is the sum of an individual's own reproductive success as well as the reproductive success of all related individuals, so sacrificing yourself for your relatives may enhance fitness.
C) The probability of self-sacrifice increases as anonymity increases, so it is considered to be pure altruism and is uniquely human.
D) Inclusive fitness is the sum of all reproductive successes, and when that amount is high enough, then the individual is free to sacrifice itself for the good of the species.