If an animal has two legs then crosses the road and has four legs then crosses the road again and has eight legs. what is the

First the man crossed the road to meet his wife who was already on the other   side (2 legs)
then ,their dog,who saw them on the other side ,decided to join them (4 legs)
and finally,the couple brought the dog home and tied it inside (8 legs)

17 is c. congruent means equal in size