Crystal structures with ions must have .a. a positive chargeb. a negative chargec. electrical neutralityd. a 2+ charge

c. electrical neutrality.

Explanation:

A crystalline  solid possesses a rigid and long-range order; its atoms, molecules, or ions occupy  specific positions. The arrangement of such particles in a crystalline solid is such that  the net attractive intermolecular forces are at their maximum.

Ionic crystals, particularly, have two important characteristics:

(1) They are composed of charged species.

(2) Anions and cations are generally quite different in size.

The forces holding the atoms together are electrostatic attractions. Examples of these types of crystals include NaCl, LiF, MgO, CaCO₃.

Since they are composed of anions and cations, in stoichiometric amount, they are to be said electrically neutral.