The correct answer is C. 7.35.
Venous blood is slightly acidic, with a pH of 7.35-7.40. This is because it contains more carbon dioxide than arterial blood. Carbon dioxide is a waste product of metabolism, and it is transported in the blood by hemoglobin. When hemoglobin binds to carbon dioxide, it forms a compound called carbaminohemoglobin. Carbaminohemoglobin is a weaker acid than hemoglobin, so it causes the pH of the blood to decrease.
Arterial blood, on the other hand, has a pH of 7.40-7.45. This is because it contains less carbon dioxide than venous blood. Arterial blood is also oxygenated, which makes it more alkaline than venous blood.
The pH of blood is important because it affects the function of many enzymes and proteins in the body. If the pH of blood deviates too far from the normal range, it can lead to serious health problems.