What is a Beaver’s tail used for

The tail is used as a rudder in swimming, as a balance prop while working on land and to signal danger when slapped on the water. Beavers will also store fat in their tails, eating more in the fall so they can survive off the fat stored in their tails through winter if food is not available.

Explanation:

this is math not biology xd

"a.) well–developed vascular system."