D is the correct answer because frog is an amphibian. When they use skin inside water and lungs on water. They have also cutaneous respirations.

Explanation:

Frogs are unique among the given options as they have the ability to breathe through their skin as well as through their lungs. Let’s explore this in detail:

1. Breathing through skin:
Frogs have a specialized skin that allows them to exchange gases with their environment. They have a thin and moist skin that is permeable to gases, allowing oxygen to enter their body and carbon dioxide to exit. This process is called cutaneous respiration.

The skin of the frog is highly vascularized, meaning it contains a network of blood vessels close to the surface. This allows for efficient gas exchange between the environment and the frog's bloodstream. Oxygen from the air diffuses through the skin and enters the bloodstream, while carbon dioxide produced by the frog's cells diffuses out of the bloodstream and into the surrounding environment.

2. Breathing through lungs:
Frogs also possess lungs, which are a pair of respiratory organs located in the chest cavity. The lungs are responsible for the majority of the frog's gas exchange, especially during periods of increased activity or when oxygen levels in the environment are low.

When a frog breathes through its lungs, it uses a mechanism called positive pressure breathing. This means that the frog actively pushes air into its lungs by lowering the floor of its mouth, drawing air in through its nostrils. The air then passes through the lungs, where oxygen is absorbed into the bloodstream and carbon dioxide is expelled.

3. Dual respiratory system:
The ability to breathe through both the skin and the lungs allows frogs to adapt to different environments. When in water, frogs primarily rely on cutaneous respiration, as their skin is constantly moist and provides a large surface area for gas exchange. On land, they primarily use their lungs to breathe, as the air is less dense and contains higher concentrations of oxygen.

This dual respiratory system is advantageous for frogs as it ensures a constant supply of oxygen regardless of their surroundings. It allows them to inhabit a variety of habitats, including both aquatic and terrestrial environments.

In conclusion, frogs possess the unique ability to breathe through their skin as well as through their lungs, making them the correct answer to the given question.