Final answer:
Gabriel's pneumonia is an opportunistic infection common in AIDS patients due to their weakened immune systems, often leading to potentially fatal outcomes. The correct answer is option C.
Step-by-step explanation:
Gabriel's pneumonia, caused by the fungus Pneumocystis jirovecii, is an example of an opportunistic infection. These infections are common in individuals with weakened immune systems, such as those with Acquired Immunodeficiency Syndrome (AIDS). Because the immune system is compromised, it provides an 'opportunity' for pathogens that would not normally cause disease in healthy individuals to infect the host. Opportunistic infections, including pneumocystis pneumonia, are frequently the direct cause of death in people with AIDS.