The hydride with lowest acid strength among the following is

The given compounds are hydrides of Group 16 elements.

As we move down the group, the atomic size of the central atom increases. This causes the bond length of the E-H bond (where E is the Group 16 element) to increase and the bond dissociation enthalpy to decrease.

Consequently, the tendency to release an $H^+$ ion increases down the group, leading to an increase in acidic strength.

The order of acidic strength of Group 16 hydrides is $H_2O < H_2S < H_2Se < H_2Te$.

Therefore, $H_2O$ has the lowest acid strength.

Answer: $\text{H}_2\text{O}$