What are investigations about an incident mainly used for? to evaluate any cost damage that occurred as a result of the incident
to prosecute the person who is responsible for the incident
to understand reasons why an incident has occurred
to end the employment of the person responsible for an incident

To understand reasons why an incident has occurred

Explanation:

When we talk about the incident investigation, we usually think about the investigation of incidents at the workplace. The term incident refers to an occurrence arising in the course of work that resulted in (or could have resulted in) injuries, illnesses, or fatalities.

The purpose of the incident investigation is to understand the reasons why an incident has occurred - to identify its causes and find ways to prevent the incident from happening again.