Answer is 3.
Andy’s statement is incorrect since penguins are birds and breathe through lungs rather than gills.
Bernie’s statement is correct but irrelevant to how penguins deal with their cold environment. Penguins have a streamlined body shape (the head is much smaller than the body). Since penguins swim forwards with the head in front, the smaller surface area will reduce the amount of resistance it faces when swimming.
Caimei’s statement is correct as penguins’ feathers are densely packed (many feathers within a small surface area). Because their feathers are so dense, it looks like fur! These feathers (together with a layer of fat under their skin) help penguins to keep warm.
Daud’s statement is correct in that penguins will huddle together, forming groups to help each other keep warm. Forming these groups also prevents them from being blown away by the strong winds.