Three monoprotic acids have the following acid-dissociation constants at 25 °C:
Acid X: Ka=1×10−5
Acid Y: Ka=4×10−4
Acid Z: Ka=6×10−8
Which of the following correctly ranks the conjugate bases (X⁻, Y⁻, Z⁻) from strongest to weakest?
a) X−>Z−>Y−
b) Z−>X−>Y−
c) Y−>X−>Z−
d) X−>Y−>Z−