What goes through the cell cycle faster, a skin cell or a heart cell?

Skin cells go faster in cell cycle than heart cells because our skin cells divide rapidly through the process called mitosis. And our skin cells divide rapidly in order to maintain protective barrier against infection. The outer skin layer is called epidermis and contains mostly dead cells that contain keratin. Keratin is tough fibrous proteins are found in hair, skin and calluses, and act as a protective coating. The epidermis cells constantly undergoing mitosis so that the outer dead cells containing keratin are rapidly replaced as they fall off which occur after so many days. Then the newer living cells start producing keratin, lose their cellular content and die and the cycle goes on.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.