What system maintain the pH of human blood at very near 7.4?

The correct answer to this question is "The Buffer System." The system that maintain the pH of human blood at very near 7.4 is called the buffer system. The buffer effect don't allow the blood to change its pH. A buffer solution is typically composed of a weak acid and its conjugate base.

Buffer systems in our body maintain the pH of blood to be at an optimum level which is at a range of 7.3-7.4. A buffer is a solution that resists changes in pH during the addition of an acid or a base. Our blood has a number of buffer systems. Examples are the bicarbonate buffer system and the hemoglobin buffer system.