Birds, such as owls and eagles, have feathers and thin, hollow bones. Reptiles, such as snakes and lizards, have scaly skin and are ectothermic animals. Both possess a unique kind of egg called the amniotic egg.
Choices 1, 2, and 3 all emit carbon dioxide, not enough to destroy the planet, but they still can cause it over a large amount of time, due to Carbon Dioxide being a greenhouse gas. Therefore, the answer is 4. Bicycles do NOT emit any carbon dioxide at all.
