Is a eal mammal reptile or amphibian?

This question is a bit tricky! There's a typo in your question. You probably meant to ask:

Is an eel a mammal, reptile, or amphibian?

Here's the breakdown:

* Eels are not mammals. Mammals have fur or hair, give birth to live young, and nurse their offspring. Eels have scales and lay eggs.

* Eels are not amphibians. Amphibians start life in water with gills, then develop lungs and live on land. Eels live entirely in water.

* Eels are fish. They have scales, fins, and gills.

So, the answer is none of the above. Eels are a type of fish.