The answer is B. Platypus, as they are mammals that lay eggs.
This process requires large volumes of water to pass through absorption surfaces to get enough oxygen into their bodies using their mouths and gills. These body parts work like a pump to keep water moving over the gas absorption surfaces of the gills.
They both may have gone to a chilly area from their instincts.
Zero of the offspring will be bb. Since each offspring receives one allele from each parent, all will receive a B from Dad and a b from Mom, making all of the offspring heterozygous (Bb) and brown-eyed.