Which of the following is a viviparous organism?

Whales are viviparous mammals that give birth to live young after gestation. Dog-fish (sharks) are typically ovoviviparous or viviparous depending on species, but whale is the clearer mammalian example. Ostrich is oviparous (lays eggs), and snakes are mostly oviparous. The question tests knowledge of mammalian reproduction.