After an HIV infection, the body of the patient starts becoming immunodeficient mainly due to :

Progressive decline in the number of helper T- lymphocytes

The correct answer is Option (3) - Progressive decline in the number of helper T-lymphocytes

In HIV (Human Immunodeficiency Virus) infection, the progressive decline in the number of helper T-lymphocytes (also known as CD4+ T cells) is a key factor that leads to immunodeficiency. Helper T-cells play a crucial role in coordinating the immune response, including stimulating B-cells to produce antibodies and activating killer T-cells to target infected or foreign cells. When the number of helper T-cells decreases, it weakens the immune system's ability to mount an effective defense against infections, making the individual susceptible to opportunistic infections and other health complications.