Which of the following statements explain why red blood cells
(rbcs) are highly specialized for oxygen transport?
(1) rbcs contain hemoglobin.
(2) rbcs lack a nucleus.
(3) rbcs have many mitochondria and thus generate atp aerobically.
(4) the biconcave shape of rbcs provides a large surface area for the inward and outward diffusion of gas molecules.
(5) rbcs can carry up to four oxygen molecules for each hemoglobin molecule.

(a) 1, 2, 3, and 5 (b) 1, 2, 4, and 5 (c) 2, 3, 4, and 5

(d) 1,3, and 5 (e) 2, 4, and 5