What Does Sober and Wilson's (1998)notion of Group Selection Propose

What does Sober and Wilson's (1998) notion of group selection propose?

A) Helping may be based on social connections rather than genetic relatedness.
B) Helping occurs when the rewards of helping are equal to the costs of not helping.
C) As the size of a group increases,helping behaviours decrease.
D) Groups are more likely to invoke reciprocal altruism than are individuals.