Calcium is a metal, sulfur is not, thus ionic bonds form creating a giant ionic lattice.
They will want you to say something like: "Strong electrostatic forces of attraction between positive and negative ions, which require a large amount of energy to overcome."
It makes sense for it to be in that order: "Strong electrostatic attraction between positively and negatively charged ions" vs: "Positively and negatively charged ions experience strong electrostatic attraction" sounds a bit weak.
If you're worrying about the order, don't, I'd instead suggest to really understand what's going on with ionic bonding then it'll come naturally.
It makes sense for it to be in that order: "Strong electrostatic attraction between positively and negatively charged ions" vs: "Positively and negatively charged ions experience strong electrostatic attraction" sounds a bit weak.
If you're worrying about the order, don't, I'd instead suggest to really understand what's going on with ionic bonding then it'll come naturally.