有甲、乙、丙三种溶液，甲能使紫色石蕊变蓝，乙能使紫色石蕊变红，丙中无现象，这三种溶液的pH由小到大的是                                   [ ]

A．甲、乙、丙        

B．乙、丙、甲       

C．甲、丙、乙          

D．丙、甲、乙