(H - E) is maximum at a given temperature in case of

PCl5(g) PCl3(g) + Cl2(g)
	2.	CaCO3(s) CaO(s) + CO2(g)
	3.	NH4HS(s) NH3(g) + H2S(g)
	4.	N2(g) + O2(g) 2NO(g)

I think you must have forgotten that H and E are related by 

Hence, the difference will be maximum when the difference in the number of moles of the gaseous product and gaseous reactant is maximum, which is maximum for the third option, as it is equal to 2. Hence 3 is the right option.