Merv Grazinski, driving his Winnebago, put it on cruise control to go make coffee. The Winnebago went off the road, turned over several times, and left Grazinski paralyzed from the waist down. He brings a product liability lawsuit against Winnebago. Which of the following is the best possible defense for Winnebago to use at trial?

Res ipsa loquitur

Contributory negligence

Assumption of risk

Proximate cause