To solve this problem, we need to identify which of the given conditions are autoimmune disorders. Let's analyze each condition:$\newline \bullet$A. Myasthenia gravis:$\newline$ - Myasthenia gravis is an autoimmune disorder where antibodies attack the communication between nerves and muscles, leading to muscle weakness.$\newline$ - Therefore, it is an autoimmune disorder.$\newline \bullet$B. Rheumatoid arthritis:$\newline$ - Rheumatoid arthritis is an autoimmune disorder characterized by inflammation of the joints due to the immune system attacking the body's own tissues.$\newline$