The wing of a bat, the arm of a human, and the flipper of a whale are structurally different even though they have similar bone structure. what is the main reason for these structural differences?

You find a fossil that you are sure shows evidence of bipedalism. you know this because which of the following anatomical traits is present? a. thighbones that angle in toward the knees b. a narrow pelvis c. opposable hallux d. posterior position of the foramen magnum