Rheumatoid arthritis is caused when:

The correct answer is Option (3) → Body attacks self cells

Option (1) Lymphocytes become more active — Incorrect. More active lymphocytes are a normal part of fighting infection. Rheumatoid arthritis happens because the immune system fails to tell self from non-self, not just because lymphocytes are more active.

Option (2) More antibodies are produced in the body — Incorrect. Producing more antibodies is the normal response to a pathogen. The problem in rheumatoid arthritis is that the immune response is turned against the body’s own cells; it is an autoimmune disease.

Option (3) Body attacks self cells — Correct. In rheumatoid arthritis the immune system fails to tell self from non-self and attacks the body’s own cells, here in the joints. This is an auto-immune disease.

Option (4) Deficiency of minerals occurs in the body — Incorrect. Rheumatoid arthritis is not a deficiency disease. It is an autoimmune disease, in which the body attacks its own cells.

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.”