NaOH、Ba（OH）₂和Na₂CO₃三种溶液，试用一种试剂把它们鉴别开来，这种试剂是(   )                                                                                                                                                       

A．稀盐酸

B．稀硫酸

C．硝酸银溶液

D．氯化镁溶液