Given below are two statements: One is labelled as Assertion A and...

The correct answer is option (3) as nearly $20-25$ precent of $\mathrm{CO}_2$ is transported by RBCs whereas 70 percent of it is carried as bicarbonate. About 7 percent of $\mathrm{CO}_2$ is carried in a dissolved state through plasma. The binding of $\mathrm{CO}_2$ with haemoglobin is related to the partial pressure of $\mathrm{CO}_2 . \mathrm{pO}_2$ is a major factor which could affect this binding. When $\mathrm{pCO}_2$ is high and $\mathrm{pO}_2$ is low as in the tissues, more binding of $\mathrm{CO}_2$ occurs. Percentage of a gas transported depends upon its partial pressure. If partial pressure decreases, the transportation of gases also decrease with haemoglobin. So, Reason is the correct explanation of Assertion.