Question

Why is a skin graft necessary when cells are damaged by a third-degree burn?
to promote the repair of existing cells
to protect the area from infection
to prevent mutations
to replace damaged nerves

Answer 1

to protect the area from infection

Third-degree burns destroy the skin's regenerative layers, so the wound can't re-epithelialize on its own. A skin graft provides new tissue to cover the wound, restoring the skin barrier, preventing infection and fluid loss, and allowing healing (and later functional/cosmetic recovery).