I think the hydra lacks the specialized cells for touch and chemical detection. On the other hand earthworms have touch, light, vibration and chemical receptors along the entire body surface. Both of them are invertebrates (those animals without a backbone), they include insects, worms, jelly fish, spiders among other animals.
all cells look the same.
rest of the options are a part of the cell theory.
A frog is an amphibian so it survive both on land and water
Hope this helps:)
