Here's why it's not the other options:
* Insect: Insects have six legs, a hard exoskeleton, and three body sections (head, thorax, abdomen). Snails have a soft body and a shell.
* Bird: Birds have feathers, wings, and lay eggs. Snails have neither of these.
* Fish: Fish live in water and have gills for breathing. Snails breathe air.
* Mammal: Mammals have fur or hair, give birth to live young, and nurse their babies with milk. Snails lay eggs and don't have fur or hair.