Which Is an Example of a Darwinian Puzzle

Multiple Choice

Which is an example of a Darwinian puzzle?

A) Salmon can smell a few molecules of chemicals in the stream in which they were born.
B) Adult birds scream in pain when caught by a predator.
C) If two or even three eggs are added to a bird's nest, the adult birds often can rear them successfully along with their own chicks.
D) Bats can catch moths in complete darkness thanks to their ability to hear echoes from their own cries.