Lungs in humans and many other species branch out into many tubes until they end in small sacks called alveoli. These alveoli allow oxygen to enter the blood through the capillary beds as pictured above. Alveoli provide much more surface area for the lungs to contact the capillary beds. What is the advantage of lungs with alveoli compared to lungs without alveoli? a Alveoli allows blood to flow into the lungs without the organism coughing up blood. b Alveoli allow the blood to thicken before receiving the oxygen. c Alveoli allows oxygen to enter the blood without the blood passing through the heart. d Alveoli allow more oxygen to enter the blood per breath.