CONCAVE SURFACE OF MAMMALIAN R B Cs IS HEIPFUL IN ....1] FORMATION OF MORE HAEMOGLOBIN 2] INCREASING SURFACE AREA OF R B Cs 3] REDUCING SURFACE TENSION OF PLASMA MEMBRANE 4] PROVIDING MORE SPACE FOR HAEMOGLOBIN
Option 2 is right.
Concave surface of mammalian RBC s is helpful in increasing surface area of RBCs.