Joe Deer Hunter falls from a tree stand manufactured by the Never-Fall Tree Stand Company, Inc. Joe wants to sue and includes a count for strict liability in tort. Which of the following is NOT one of the three things Joe must prove in a strict liability case? (a) that the manufacturer was negligent; (b) that the product was defective when sold; (c) that the product was the cause of Joe’s injury; (d) that the defect rendered the product unreasonably dangerous.