Which of the following is a characteristic of extravascular hemolysis?

Extravascular hemolysis is primarily characterized by the destruction of red blood cells (RBCs) by macrophages, which are part of the mononuclear phagocyte system. This process typically occurs in the liver, spleen, and bone marrow. In extravascular hemolysis, aged or damaged RBCs are recognized and engulfed by macrophages, leading to their breakdown. This mechanism is a normal physiological response and is critical for the removal of senescent or abnormal RBCs without significant hemolysis occurring in the bloodstream.

In contrast, other options represent different mechanisms of hemolysis. The activation of the complement cascade is more associated with intravascular hemolysis, where complement-mediated lysis occurs. Increased osmotic pressure leading to lysis pertains to conditions like hypotonic environments causing RBCs to burst, which is also not typical of extravascular hemolysis. Lastly, the direct rupture of RBCs in the bloodstream describes intravascular hemolysis, not extravascular. Thus, the key characteristic of extravascular hemolysis being the role of macrophages underscores the correct answer.