单选题:According to the passage.why couldn't PET and functional M.R 题目分类:2级 题目类型:单选题 号外号外:注册会员即送体验阅读点! 题目内容: According to the passage.why couldn't PET and functional M.R.I.scans detect subtle changes in blood flow earlier? 参考答案: 答案解析: