CAP, a small child, found a cigarette lighter on the floor in his father's truck. He lit the lighter, his shirt caught on fire, and he was burned from the waist up$.$ CAP received treatment for second and third degree burns to his face and chest and underwent several skin graft surgeries. The lighter CAP used was worn and the legally required child safety guard had been removed from the lighter. CAP's father, Thor, acknowledged that he usually bought BIC lighters and customarily removed the child$-$resistant guards from them to make them easier to use. What defense to a product liability lawsuit brought by CAP is appropriate?

Assumption of risk

Res ipsa loquitur

Product misuse

Superseding event