$T$-cells mature in the . . . . . . .

Which one of the following groups is associated with secondary lymphoid organs?

Animals develop immunity in their bodies to combat diseases during their lifetime after birth. This is called.........

What does $CMI$ stand for?

In higher vertebrates, the immune system can distinguish between self and non-self cells. Due to genetic or other unknown reasons, the immune system sometimes loses this property and starts attacking self-cells, resulting in:

Identify $X$ from the given figure.