Which piece of evidence best supports the hypothesis that the evolution of altruistic behavior is driven by kin selection?

Question

A meerkat protects the offspring of its sister from an attack by hawks.

A cuckoo bird hides its own eggs in the nest of another bird species.

A male gorilla helps protect his offspring from an attack by a tiger.

A hippo is observed saving an antelope from an attack by an alligator.

Answer 1

A meerkat protects the offspring of its sister from an attack by hawks.