<prompt> Life span of RBC is:100 days120 days60 days160 days  <response>: Ans: b 120 days Ref: Ganong,22nd ed, p. 532In humans RBC survive in circulation for an average of 120 days.Remember Average life span of RBC- 120 daysAverage life span of neutrophil- 6 hoursAverage life span of platelets- 4 daysAverage life span of transfused platelets- 1 dayMonocytes as tissue macrophages-3 months according to Bone marrow transplantation data. 