Jk(a-b-) red cells are __________ to lysis in 2 M urea.

The correct answer indicates that Jk(a-b-) red blood cells are resistant to lysis in a 2 M urea solution. This resistance is due to the specific membrane characteristics of these red cells, which maintain their integrity even in the presence of high concentrations of urea.

Jk(a-b-) phenotype refers to the absence of the Kidd antigens on the red blood cell surface. The Kidd blood group system plays a key role in cell membrane stability and function, and red cells lacking these antigens exhibit strong resilience in hypertonic solutions. In the context of urea lysis, resistant cells do not undergo hemolysis because their structural makeup and ionic membrane composition provide a protective barrier, unlike cells that show sensitivity and would break down under similar conditions. Thus, understanding the properties of specific blood group antigens and their effects on red cell membrane stability is crucial in hematology and transfusion medicine.

The other choices do not accurately describe the behavior of Jk(a-b-) red cells in this scenario. Being susceptible or sensitive would imply an inclination to hemolysis in response to urea exposure, which is contrary to the behavior observed in these red cells. The term "reactive" does not apply specifically to the context of