Question

1. which of the following is the main factor that controls the rate of breathing? concentration of carbon dioxide stimulating the cerebral cortex displaying emotions drug and alcohol levels

Explanation:

The main factor controlling breathing rate is the concentration of carbon dioxide ($CO_2$) in the blood. When $CO_2$ levels rise, it lowers blood pH, triggering chemoreceptors to signal the respiratory center to increase breathing rate to expel excess $CO_2$. Other options (cerebral cortex stimulation, emotions, drugs/alcohol) are secondary or modifying factors, not the primary controller.

Answer:

concentration of carbon dioxide