A,B,X and E are 16th group elements of Modern periodic table. The correct trend of bond enthalpy is A-H > B-H > X-H > E-H. The element ‘X’ in the sequence is

Down the group as the size of the atom increases affinity of hydrogen towards central atom decreases. Thereforea) X-H bond enthalpy decreases….O-H>S-H>Se-H>Te-H;b) Thermal stability decreases….H2O>H2S>H2Se>H2Te;H2O and H2S are exothermic products, remaining three hydrides are endothermic products.c) Reducing power increases…..H2OH2S>H2Se>H2Te;Down the group as vanderwaal's forces increasesMelting and boiling points increasesExpected BP and MP….H2OH2S>H2Se>H2Te;