What is a burner in the context of a retort?

In the context of a retort, a burner refers specifically to the device responsible for introducing flame into the primary chamber of the cremation retort. This critical component is essential for the cremation process, as it provides the heat necessary to reduce the remains to ash. The burner ensures that the combustion is efficient and effective, allowing for the complete and respectful cremation of remains.

Given this function, it is clear why the correct answer focuses on the role of the burner in flame introduction; it is integral to the operation of the cremation equipment and directly impacts the process being carried out within the retort. Without the burner, the cremation process could not occur.