What was the purpose of reconstruction

How can hind limbs be used to tell alligators and crocodiles apart? a. alligators have jagged fringe on their legs and feet, crocodiles do not. c. i don't want to get close enough to find out! b. crocodiles have jagged fringe on their legs and feet, alligators do not. d. alligators have webbed feet, crocodiles have individual toes