Explain the advantages of red blood cells passing through a capillary one at a time (3 Marks)

Red Blood Cells (erythrocytes) are approximately 0.01 mm, so only one can pass through the small capillary. The advantage of this is that there is a larger surface area exposed, more time available and shorter difference for exchange of oxygen. This way, oxygen can be released to the tissues, or taken up from the lungs.