The most acidic and thermally stable hydrides of chalcogens are respectively;

 The hydride of oxygen has the greatest thermal stability, whereas tellurium has the least. It is because the dissociation energy of the link between the elements and hydrogen lowers as the size of the atom at the center increases. The most acidic hydride of the group 16 elements is surely the hydride of tellurium.

Hence, the correct answer is option (D) ${\mathrm{H}}_2\mathrm{Te},{\mathrm{H}}_2\mathrm{O}$.