Correct Answer - Option 4 : Heart
Animal always has:
1) Fur: This is not necessary that all animals have fur.
For Example naked mole rats, Mammals.
2) Wings: Each animal does not have wings.
Animals that have wings are insects, birds, and bats.
3) Horns: Some animal does not have horns.
Animals having horns are goat, rhinoceroses, cow, bull, and buffalo.
4) Heart: This is necessary that each animal having a heart always.
Hence, "Heart" is the correct answer.
