Ionic bonds result from elements . A. that share electrons
B. with high electronegativity differences
C. That form polar bonds
D. That are only nonmetals

Ionic bonds are a class of chemical bonds that result from the exchange of one or more valence electrons from one atom, typically a metal, to another, typically a nonmetal. This electron exchange results in an electrostatic attraction between the two atoms called an ionic bond.
So I would think A

Because a model would make the investigation easier to understand