Choose all of the characteristics from the list below that are examples of adaptations common among all birds.

(1) backbone

(2) cold-blooded

(3) give live birth to offspring

(4) sharp teeth

(5) solid bones

(6) four legs or feet

(7) feathers

(8) hollow bones

(9) warm-blooded

(10) four-chambered heart

(11) lay hard-shelled eggs

(12) two legs or feet

(13) soft-shelled eggs

(14) two-chambered heart