The two brothers look so much alike that it is difficult to      .

A．tell them from

B．tell from them

C．tell them apart

D．tell apart them

下列除杂（括号内的是杂质）所选试剂合理的是[ ]

A．Cu（Zn） 稀盐酸             

B．CO₂气体（HCl） 氢氧化钠溶液

C．NaCl（Na₂CO₃） 硝酸钠        

D．CaCl₂溶液（HCl）氢氧化钾溶液