All of the above... I feel u must go through the diagram of RS... may be it get more .. clear

Organs of the Human Respiratory System

The respiratory system is responsible for the exchange of gases, such as oxygen and carbon dioxide, between the body and the environment. It consists of several organs that work together to facilitate this process. The organs of the human respiratory system include the trachea, bronchus, and alveolus.

1. Trachea:
The trachea, also known as the windpipe, is a tube-like structure that connects the larynx (voice box) to the bronchi. It is composed of rings of cartilage that provide support and prevent the trachea from collapsing. The trachea allows air to pass through it, facilitating the movement of air into and out of the lungs.

2. Bronchus:
The bronchi are the main airways that branch off from the trachea and enter the lungs. They further divide into smaller tubes called bronchioles. The bronchi are responsible for conducting air into the lungs, allowing it to reach the alveoli.

3. Alveolus:
The alveoli are tiny air sacs located at the end of the bronchioles within the lungs. They are surrounded by a network of capillaries, which are small blood vessels. The alveoli are the site where gas exchange occurs. Oxygen from the air diffuses into the bloodstream through the thin walls of the alveoli, while carbon dioxide, a waste product, diffuses out of the bloodstream into the alveoli to be exhaled.

Conclusion:
The organs of the human respiratory system play vital roles in the process of respiration. They work together to ensure the exchange of gases necessary for sustaining life. The trachea allows air to flow into and out of the lungs, the bronchi conduct air into the lungs, and the alveoli are responsible for the exchange of gases between the air and the bloodstream. Therefore, the correct answer is option 'D' - all of these organs are part of the human respiratory system.