Answer: The correct answer for the blank is-
tadpole or larvae.
Explanation:
During the metamorphosis (that is transformation of immature egg to adult forms) in amphibians such as frogs, there occur four stages that are egg, tadpole, froglets, and adult.
Amohibians such as frogs, when hatch from egg, they begin life as tadpoles, which are tiny aquatic larvae, having external gills for respiration and are mainly vegetarian.
As they grow, limbs and internal gills are formed and they transform to froglets, which further undergo some developmental changes to give adult forms.
Thus, tadpole or larvae is the right answer.
