Final answer:
The statement that air pressure and air density decrease together is true. Air pressure and density are directly related; as one decreases, typically so does the other. This relationship is particularly significant when considering altitude's impact on air composition and physiological processes such as breathing.
Step-by-step explanation:
The statement As air pressure decreases, so does air density is true. Air density is directly related to air pressure; when air pressure decreases, such as with an increase in altitude, the density of the air also decreases. This decrease in air density with altitude can be represented by an exponential function when the temperature is constant. However, the temperature does often change with altitude, which can affect this relationship. Air pressure and air density are fundamental to understanding various physical and physiological phenomena. For instance, the density of air affects the oxygen concentration, which has implications for pulmonary ventilation and the performance of athletes at high altitudes. Bernoulli's equation also reflects the relationship between pressure, fluid density, and flow rate, further highlighting the importance of understanding these physical properties.