What is the primary function of platelets in the blood?

A. Trachea: The trachea is part of the lower respiratory tract. It conducts air between the larynx and bronchi and provides a passageway for airflow into the lungs.

B. Alveoli: Alveoli are tiny air sacs within the lungs where gas exchange occurs. They are located in the lower respiratory tract and are not part of the upper airway.

C. Bronchi: The bronchi branch from the trachea into each lung. They are considered part of the lower respiratory tract, directing air toward the alveoli.

D. Pharynx: The pharynx, located behind the nasal and oral cavities, is part of the upper respiratory tract. It serves as a pathway for air from the nose and mouth to the larynx and trachea.

A. Photoreceptors: Photoreceptors are specialized cells in the retina that detect light and color, playing a role in vision. They do not respond to temperature changes.

B. Chemoreceptors: Chemoreceptors detect chemical changes in the environment or body, such as oxygen, carbon dioxide, and pH levels. They are not involved in sensing temperature.

C. Thermoreceptors: Thermoreceptors are sensory receptors located in the skin and hypothalamus that respond to changes in temperature. They allow the body to perceive warmth and cold and help regulate thermoregulation.

D. Mechanoreceptors: Mechanoreceptors respond to mechanical stimuli such as pressure, touch, vibration, and stretch. They do not detect temperature changes.