The shape of a RBC increases both __ and __ to allow a better transport of O2& CO_(2) square footage/yards parallel velocity/horizontal area diameter/length surface area/volume

The shape of a red blood cell (RBC) increases both its surface area and its volume to allow for better transport of oxygen (O2) and carbon dioxide (CO2). The biconcave shape of the RBC increases its surface area, which allows efficient gas exchange. The increased volume of the RBC also allows for more oxygen to be carried within the cell. Therefore, the correct answer is surface area/volume.