Final answer:
Older individuals are at increased risk for autoimmune diseases, hypersensitivity reactions, and infections due to a decline in immune system functionality, which supports the answer '4) All of the above'.
Step-by-step explanation:
Older individuals are at increased risk for a variety of problems related to the immune system, including autoimmune diseases, hypersensitivity reactions, and infections. As people age, their immune system does not function as effectively as it used to, which can lead to a higher susceptibility to diseases. Autoimmune diseases occur when there is a loss of immune tolerance, and the body's immune system begins to attack its own tissues. These diseases are associated with type II, III, and IV hypersensitivity reactions. Moreover, the incidence of infections tends to be higher in the elderly due to a decline in immune response capability. Therefore, the correct answer to the question is '4) All of the above'.