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有气泡逸出 ；③ ④ 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  ③ ④ ②①           D  ③ ① ②④  

--- Have you got any particular plans for the coming holiday?

--- Yes. ________, I’m going to visit some homes for the old in the city.

A．If possible

B．If ever

C．If busy

D．If anything