—Mary and Betty look exactly the same to me.  

—Oh, sometimes I also find it hard to tell one from _________.  [ ]

A. another

B. other

C. the other

D. the others

可以验证硫元素的非金属性比氯元素弱的事实是

①H₂S水溶液是弱酸，HCl水溶液是强酸  ②向氢硫酸溶液中滴入氯水有单质硫生成  ③硫、氯气分别与铜和铁反应，其产物是FeS、Cu₂S、FeCl₃、CuCl₂     ④高氯酸（HClO₄）的酸性比硫酸强

A．②③④

B．②④

C．①②④

D．①②③④