Concept:Blood buffers are chemical systems that keep blood pH stable by neutralising excess acids or bases.
Explanation:The major buffering system in blood is found in the fluid part of blood, which is called plasma.
Plasma contains dissolved bicarbonate ions and proteins that act as buffers.
These buffers combine with excess hydrogen ions or hydroxide ions to prevent large changes in pH.
Erythrocytes, or red blood cells, contain haemoglobin, which helps buffer mainly inside the cells, but plasma is the major buffer site in whole blood.
Leucocytes are white blood cells for immunity, not for buffering.
Lymph is tissue fluid, not the main blood buffer.
Therefore, the correct component is plasma because it carries the principal buffering substances of blood.
Answer:A. plasma