Some animals return to water bodies to reproduce because

Analyze the question: It asks why some animals (e.g., amphibians such as frogs and toads, and some fish) go back to water to reproduce.

Concept: Amphibians evolved from aquatic ancestors. Their eggs have no shell and no waterproof membranes, only a jelly-like covering. Because of this, the eggs dry out quickly on land. They need water to stay moist, to allow fertilisation (external fertilisation in frogs), and to support the development of the embryo into a larval stage (tadpole). The tadpole breathes with gills and can only live in water. So water provides the right environment for the embryos and young ones to develop.

Evaluating the options:

• A. Natural enemies destroy their eggs on land: Predators exist in water too, so this is not the main reason.
• B. Water nourishes their embryos and their young ones: This is the best fit. Water supports the eggs and larvae, provides moisture, oxygen, and food (such as algae and microorganisms for tadpoles), and is the medium in which they develop.
• C. They are close to their ancestors and imitate them: Animals do not reproduce by imitation. It is not a scientific explanation.
• D. The temperature on land is not suitable: Temperature is not the main reason. The real problem on land is desiccation (drying out), not temperature.

Answer: B. Water supports and nourishes the embryos and young ones.

Exam tip: For "why do amphibians return to water to breed" questions, think of three things: moist, shell-less eggs, external fertilisation, and aquatic larvae (tadpoles with gills). Whenever you see the word "water" paired with "embryo/young ones" in the options, it is usually the right choice. Ignore options that mention "imitating ancestors"; such options are usually distractors.