Altruism at First Was a Puzzle to Evolutionary Biologists Because

Multiple Choice

Altruism at first was a puzzle to evolutionary biologists because it should

A) be more common in nature because it increases the fitness of recipients.
B) be more common in nature because it increases the fitness of species.
C) not be common in nature because it decreases the fitness of actors.
D) not be common in nature because it decreases the fitness of species.