Iowa residents Robert and DeAnn Wright sued various cigarette manufacturers in a federal district court in an effort to obtain damages for harms allegedly resulting from Robert's cigarette smoking. The plaintiffs pleaded a number of alternative claims, including strict liability. The defendants filed a motion to dismiss, but the federal court largely overruled it. Thereafter, the defendants asked the federal court to certify questions of law to the Iowa Supreme Court, in accordance with an Iowa statute. Concluding that the case presented potentially determinative state law questions as to which there was either no controlling precedent or ambiguous precedent, the federal court certified questions to the Iowa Supreme Court regarding the use of strict liability principles in design defect cases. In answering the certified questions, the Iowa Supreme Court adopted the design defect rules proposed in the Restatement (Third) of Torts: Product Liability. Therefore, what controlling rules did that court identify in answering the certified questions? What test did it say courts should apply in design defect cases? What did it say a plaintiff in a design defect case must prove?