Which structure is directly involved in gas exchange? Trachea, pharynx, alveoli, or bronchi

How does friction with the atmosphere affect the speed of an artificial satellite

Cells destroy body cells infected by a virus or bacteria.

What is the importance of having the us forest service, the bureau of land management, the us fish and wildlife service, and the national park service? to manage land resources for conservation and the development of natural resources to manage land resources for conservation and the development of urban areas to preserve historical landmarks and manage the development of urban areas to preserve historical landmarks and manage the development of rural areas