Answer
a) More soluble in 0.1 M HCl
b) More soluble in 0.1 M NaOH
c) More soluble in 0.1 M NaOH
Work Step by Step
A more soluble substance is one that dissociates more in the given solvent.
a) Pyridine has a $pK_{a}$ of 5 and so will be more soluble in an acidic pH thus in 0.1 M HCl.
b) Beta-Naphthol has a $pK_{a}$ of 10 and so will be more soluble in an alkaline pH thus in 0.1 M NaOH.
c) N-Acetyltyrosine methyl ester has a $pK_{a}$ of 10 and so will be more soluble in an alkaline pH thus in 0.1 M NaOH.
