—Are you going to help John with his Chinese this evening? —No,He ________ to England.He will be back next month. A.returned B.has returned C.returns D.will return 答案:B如图是电解水的实验装置,回答下列问题:
(1)A试管里产生的是
气; A、B两试管内气体的体积比为 ;
(2)电解水反应的化学方程式为 ;电解水过程中,最小的微粒是 ;由该实验得出的结论 。