A difference between the A, B, and O blood types and the Rh factor is:
(a) Rh agglutinogens are not found on the surface of red blood cells
(b) Rh agglutinogens do not produce a cross-reaction
(c) Individuals who are Rh− do not carry agglutinins to Rh factor unless they have been previously sensitized
(d) Rh agglutinogens are found free in the plasma
(e) Rh agglutinogens are found bound to plasma proteins