Here it says which of the following reactions is associated with the latticed association of lithium oxide. Now with lattice association, we start out with a solid ionic compound. So we're starting out with lithium oxide solid. That means that these three are out.
And remember it's an endothermic process, so we absorb energy to break this ionic solid into gaseous ions. So they have to have charges and they have to be in their gaseous state. That means option 4, which corresponds to choice D, would be the right answer.
