Answer: Option A
Step-by-step explanation:
The immune system of the body is made of a variety of cells. The cells producing antibodies "remembers" the infection caused inside the body and helps in providing immunity against it for a very longer duration of time..
The T-cells of the immune system remembers the viruses and contains a number of phagocytotic cells which helps in proving immunity. T- cells also activates B-cells.
So, if the Number of T-cells drastically reduces in number, then the body will be more susceptible to infection.