Rheumatoid arthritis is an autoimmune disease that primarily affects the joints. The immune system mistakenly attacks healthy tissue in the joints, causing inflammation and pain.
Let's analyze each option:
(1) Alzheimer’s disease:
Alzheimer’s disease is a neurodegenerative condition but is not classified as an autoimmune disorder. Hence, this is not the correct answer.
(2) Rheumatoid arthritis:
Rheumatoid arthritis is an autoimmune disorder where the immune system attacks the joints, causing inflammation and damage. This is the correct answer.
(3) Chronic gum disease:
Chronic gum disease (periodontitis) is an inflammatory condition but is not an autoimmune disorder. Hence, this is not the correct answer.
(4) AIDS:
AIDS is caused by the HIV virus and is an immunodeficiency disorder, not an autoimmune disorder. Hence, this is not the correct answer.
Conclusion:
The correct answer is Option 2: Rheumatoid arthritis as it is an autoimmune disorder.