Rheumatoid arthritis is:

The correct answer is Option (1) → An autoimmune disease

The immune system can normally tell the body’s own cells (self) from foreign things (non-self). Sometimes, because of genetic or other unknown reasons, it starts attacking the body’s own cells. This damage is called auto-immune disease. Rheumatoid arthritis is one such disease. The immune system attacks the joints.

(1) An autoimmune disease — Correct. In rheumatoid arthritis the body’s own immune system damages the joints.

(2) A genetic disease — Incorrect. A genetic disease, like sickle-cell anaemia or haemophilia, is caused by a faulty gene or chromosome. Rheumatoid arthritis is caused by the immune system attacking self cells.

(3) An infectious disease — Incorrect. An infectious disease is caused by a pathogen such as a bacterium or virus. No pathogen causes rheumatoid arthritis.

(4) A communicable disease — Incorrect. A communicable disease passes from one person to another. Rheumatoid arthritis cannot be passed on.

NCERT Extract:
Auto Immunity – “… Memory-based acquired immunity evolved in higher vertebrates based on the ability to differentiate foreign organisms (e.g., pathogens) from selfcells. While we still do not understand the basis of this, two corollaries of this ability have to be understood. One, higher vertebrates can distinguish foreign molecules as well as foreign organisms. Most of the experimental immunology deals with this aspect. Two, sometimes, due to genetic and other unknown reasons, the body attacks self-cells. This results in damage to the body and is called auto-immune disease. Rheumatoid arthritis which affects many people in our society is an auto-immune disease.”