$\begin{array}{1 1}(a)\;H_2O>H_2Se>H_2Te>H_2Po>H_2S\\(b)\;H_2O>H_2S>H_2Se>H_2Te>H_2Po\\(c)\;H_2O>H_2S>H_2Se>H_2Po>H_2Te\\(d)\;H_2O>H_2Se>H_2S>H_2Po>H_2Te\end{array}$
