Which of the following is the weakest acid in its aqueous solution?

 Acidic character is inversely proportional to the stability of the elements with hydrogen. In group 16, the stability order is: ${\mathrm{H}}_2\mathrm{O}>{\mathrm{H}}_2\mathrm{ }\mathrm{S}>{\mathrm{H}}_2\mathrm{Se}>{\mathrm{H}}_2\mathrm{Te}$. Therefore, the

acidity order will be as ${\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{ }\mathrm{S}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}$. Thus, the weakest acid in its aqueous solution will be ${\mathrm{H}}_2\mathrm{ }\mathrm{S}$.