Had I mastered the statistic technique, a large amount of time and, energy      .

A．was avid

B．had been saved

C．will be saved

D．would have been saved

①②③④四种金属片两两相连浸入稀硫酸中都可组成原电池，①②相连时，外电路电流从②流向①；①③相连时，③为正极；②④相连时，②上有气泡逸出；③④相连时，③的质量减少。据此判断这四种金属活动性由大到小的顺序是

A．①③②④

B．①③④②

C．③④②①

D．③①②④