Which of the following best describes oxygenation?

Oxygenation refers specifically to the process of oxygen being transported into the bloodstream and becoming available for use by the body's tissues. When oxygen enters the lungs, it diffuses across the alveolar membranes and into the pulmonary capillaries, where it binds to hemoglobin in red blood cells. This essential process ensures that the body's cells receive the oxygen they need for metabolic functions.

The other options describe associated processes but do not capture the essence of oxygenation. The removal of carbon dioxide from the lungs is part of ventilation and is crucial for maintaining acid-base balance but is not synonymous with oxygenation. The exchange of gases in the alveoli encompasses both oxygen uptake and carbon dioxide removal, representing a broader process rather than focusing solely on oxygenation. Lastly, an increase in respiratory rate can occur as a response to various physiological conditions but does not inherently define the process of oxygenation itself. Thus, the best choice among the options provided is the one that directly addresses the movement of oxygen into the bloodstream.