To solve this problem, we need to identify which of the given animals is not viviparous. Viviparous animals give birth to live young rather than laying eggs. Let's analyze each option:$\newline \bullet$Option 1: Flying fox (Bat)$\newline$ - Bats are mammals and are viviparous, meaning they give birth to live young.$\newline \bullet$Option 2: Elephant$\newline$ - Elephants are mammals and are viviparous, giving birth to live young.$\newline \bullet$Option 3: Platypus$\newline$ - The platypus is a monotreme, a type of mammal that lays eggs. Therefore, it is not viviparous.$\newline \bullet$Option 4: Whale$\newline$ - Whales are mammals and are viviparous, giving birth to live young.$\newline$Based on this analysis, the animal that is not viviparous is the platypus.$\newline$Therefore, the correct option is Option 3.