Which is most soluble?

$\mathrm{AgF}$ is most soluble in water. 
A solute is a material that dissolves, while a solvent is a substance that facilitates that dissolution. For instance, the fluoride ion in Silver Fluoride $\left(\mathrm{AgF}\right)$ is the least polarized of the silver halides $\left({\mathrm{Ag}}^{+}\right)$, and as a result, it is soluble in water.
Hence, the option A is correct.