Concept:Viviparous animals give birth to live young, while oviparous animals lay eggs.
Explanation:Cow, dog, and goat are mammals that give birth to live young.
Thus, they are viviparous animals.
Pigeon is a bird that lays eggs and hatches them outside the body.
So, pigeon is oviparous, not viviparous.
Therefore, the animal that is the exception is pigeon.
Answer:D. Pigeon