The correct order of acidic character of the following is:

The acidity is directly proportional to the tendency of the hydrogen donor. It depends upon the bond dissociation enthalpy of the $\mathrm{X}-\mathrm{H}$ bond where $\mathrm{X}$ is $\mathrm{Te},\mathrm{Se},\mathrm{S} \& \mathrm{O}$. Down the group the bond dissociation energy of hydrides decreases and the acidic strength increases.

Hence, the correct order of acidic character of the given hydrides is ${\mathrm{H}}_2\mathrm{Te}>{\mathrm{H}}_2\mathrm{Se}>{\mathrm{H}}_2 \mathrm{S}>{\mathrm{H}}_2\mathrm{O}$.