Which statement shows the function of air pressure in controlling expiration?
a.) a decrease in air pressure within the lungs allows air to flow in.
b.) an increase in air pressure within the lungs allows air to flow out.
c.) a decrease in air pressure within the lungs causes them to contract.
d.) an increase in air pressure within the lungs causes them to expand.

The best and most correct answer among the choices provided by your question is the third option or letter C "A decrease in air pressure within the lungs causes them to contract."

Exhalation (or expiration) is the flow of the respiratory current out of the organism. In humans it is the movement of air out of the bronchial tubes, through the airways, to the external environment during breathing.

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stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.