9. Whether eating out will cause certain cancers has remained ______; experts are still finding evidence to prove the truth.
句意：在外吃饭是否会得某些癌症尚存争议，专家仍在寻找证据证明事实。contradictory“相互矛盾的” ；convincing “令人信服的” ；concrete“明确具体的” ；controversial“有争议的” ，只有D符合句意。
根据句子后半部分“专家还在找证据证明”，说明前半句的观点具有争议。
词义混淆。