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What is 1 + 3?
Science Chapter 3, Section 4, and Chapter 4, Section 1
an ectothermic vertebrate that has lungs and scaly skin
liquid waste that is produced in the kidneys
an endothermic vertebrate with feathers and a four-chambered heart
large feathers that give shape to a bird's body and help with flying
feathers that trap heat and keep a bird warm
material that helps to keep something warm