The correct option is
A dil.
HClIn general, acids and bases dissolve in each other. This criterion can be used to decide solubility.
Aniline is basic in nature. It will readily dissolve in hydrochloric acid.
HCl is acidic in nature and will easily for a salt with aniline
PhNH2+HCl→PhNH+3Cl− (soluble)
So, A is the correct answer.