The best piece of evidence to support the argument for kin selection as a mechanism for the evolution of altruistic behavior is:
a penguin protects its chick from seagulls.
This example directly demonstrates a parent (the penguin) exhibiting altruistic behavior towards its offspring (the chick), which is a key aspect of kin selection. Kin selection explains how individuals may act altruistically toward their relatives to increase the chances of shared genes being passed on to future generations. In this case, the penguin's behavior directly benefits its genetic offspring.