<h2><em>The trachea connects the larynx to the bronchi and allows air to pass through the neck and into the thorax. The rings of cartilage making up the trachea allow it to remain open to air at all times</em></h2>
Your question is unclear but, based on the context, it is clear to me that the point that comes after C (point D) refers to the process of evaporation. Please try to post a picture of the diagram and make your question clearer next time.
