When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?

Explanation

When lungs become concentrated with the same CO2 as in blood, it no longer leaves the blood and keeps rising. One breathes in CO2 diffuse out of lungs and oxygen is taken in. When you hold your breath there is an accumulation of carbon dioxide in your cells, in your blood and lungs it will irritate and trigger the impulses from the respiratory center part of your brain due to a rise in CO2 concentration, it signals the body to breathe and respiration. This rise in CO2 concentration also makes us sleepy. The effect of rising CO2 tension is to decrease the affinity of Hb for O2. Thus, when CO2 concentration in blood increases, breathing becomes faster and deeper.So, here the option D, i.e., rising CO2 concentration is the correct answer.