第19题: [单项选择]Eating better and eating less could be the ______ not only to avoiding cancer but also to living longer. A. key B. foundation C. rule D. importance 参考答案:A 答案解析:[解析] key to:……的关键,前面可加冠词the。
第20题: [单项选择]新生儿光疗时(蓝光),其光源的最有效波长为() A. 320~350nm B. 425~475nm C. 400~420nm D. 470~500nm E. 550~600nm 参考答案:B