I think the anwer is electrolyte :)... i had it on a test a couple days ago.
D, the energy of formation is equal to the dissociation. so from magnesium ions and Hydrogen ions, when they form the lattice energy is equal to formation-dissociation, as they aren't going to dissociate (fixed in lattice) the formation should be the same as the the overall lattice energy.
The molarity of the dilution solution is 0.050 M
<h3>Further explanation</h3>
Molarity is a way to express the concentration of the solution
Molarity shows the number of moles of solute in every 1 liter of solute or mmol in each ml of solution

Where
M = Molarity
n = Number of moles of solute
V = Volume of solution
Dilution formula :

M₁=6 M
V₁=12.5 ml
V₂=1.5 L=1500 ml

I believe the answer is 1-Water :)