Apoptosis can occur in a cell when the cell is
damaged
no longer needed
infected by a virus
all of the above

Option D. "all of the above"

Explanation:

Apoptosis is known as programmed cell death.

Apoptosis can be initiated by several ways such as when cell is damaged, when cell is no longer needed and due to virulent infection.

When cells are damaged, they kill themselves by activating procaspase aggregation within the cell.

Apoptosis is also initiated when the cells are no longer needed in our body that maintains the balance (homeostasis) of cells in the human body which are important in the immune system.

Apoptosis takes place to eliminate and control the virus, when cell is infected from any virus in order to save body from the damage caused by the virus.

Hence, the correct option is D.