A. have a very clear cornea B. have a normal cornea C. have a cloudy cornea with some diseases such as glaucoma D. have a defective cornea without any problems concerned with the optic nerve or retina 参考答案:D 答案解析:[解析]事实细节题。本题可参考文章第五段第一句:The best candidates for corneal transplants have a cloudy,scarred,or misshap