Meerkats Are Small Desert Mammals That Live in Groups of 20-50

Meerkats are small desert mammals that live in groups of 20-50 individuals. You observe the behavior of a group of meerkats. Which of the following behaviors would you categorize as examples of reciprocal altruism?

A) Two meerkats take turns grooming each other, each spending about the same amount of time grooming the other.
B) One meerkat grooms a second meerkat, who is sleeping.
C) One meerkat spends time standing upright on a stump, looking around, while other meerkats forage for food.
D) One meerkat spends time sleeping in the burrow after eating, while other meerkats forage for food.
E) One meerkat stands in the sun, while the other spends time digging out the burrow.