题目

阅读短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。 Marathon fever is sweepingthis country. In recent years, China's ever-growing passion for marathons hasbeen triggered by its economic development and health-conscious middleclass. A large number of marathon runners are white-collar workers, civilservants and business people that are keen on leading a healthy lifestyle.Government support, social participation and strong marketing by the sportsindustry have gradually led to the rapid development of the marathon industry,which is currently valued at 70 billion y9．回答下列问题（1）科学家卡尔文用14C标记CO2供小球藻进行光合作用，探明了卡尔文循环途径，请写出CO2的14C的转移过程14CO2→14C3→（14CH2O）．（2）在实验A中，如果所用的水有0.48%含18O，CO2中有0.68%含18O，则释放的氧气中含18O标记的氧原子比例为0.48%．（3）现有一瓶混有酵母菌和葡萄糖的培养液，通入不同浓度的氧气时，产生酒精和二氧化碳的量如图所示，请据图回答问题．1）曲线a表示二氧化碳量；曲线b表示酒精量．2）酵母菌呼吸作用产生酒精的场所是细胞质基质，酒精可用酸性重铬酸钾溶液鉴定．3）氧气浓度为a时，酵母菌无氧呼吸消耗的葡萄糖量占葡萄糖总消耗量的$\frac{3}{4}$．