Here we're asked which of the following species has bonds with the most ionic character. So think about it. When we talk about ionic bonding, we said it's the opposing charges of a cation and an anion. Remember the cation which is positive is usually a metal. It can also be the ammonium ion. And then remember our anion, our negative ion will be a nonmetal.
These are the fundamental definitions we talked about way back when we first covered ionic compounds versus covalent compounds. So if you don't remember that, good idea to write this down. So basically the most ionic character will be the one that fits this definition of a cation bonded to an anion. So we're looking for an example that has either a metal connected to a nonmetal or the ammonium ion connected to a nonmetal.
And if we look at our choices present, we see that the only choice has to be option C because here it has tin, which is Sn, or metal connected to oxygen, a nonmetal. So we have in this example a metal to a nonmetal. All the others don't fit the criteria to be an ionic compound because they're just nonmetals connected together. They themselves would just represent covalent compounds.