What adaptation of a bird skeletal system allows for it to be light enough to fly

The bird skeleton is extremely lightweight, but strong enough to withstand the stresses that a bird experiences when taking off, flying, and landing. The bird's hollow bones make the skeleton lighter for flying, and allow more oxygen to be absorbed from the air into the blood for that extra energy a bird needs.

B). Velocity is speed with displacement

Explanation:

Velocity's formula has displacement in it, while speed has no displacement in its formula.