Which of the following best represents an ionic equation?

An ionic equation is a representation of a chemical reaction where the compounds are shown as ions, particularly highlighting the ions that are involved in the reaction. Answer B involves the reaction of magnesium metal with sulfuric acid, forming magnesium sulfate and hydrogen gas. In this context, when sulfuric acid dissolves in water, it dissociates into its constituent ions, specifically H⁺ and SO₄²⁻. The presence of ions in these reactants is what makes this choice relevant to an ionic equation when considering the overall process.

In contrast, the other options either do not represent the dissociation of compounds into their ionic forms or do not involve ionic interactions. For example, A is a depiction of a dissociation but does not illustrate a reaction taking place. Choices C and D show molecular and compound transformations without highlighting ionic behavior, making them less suitable representations in relation to ionic equations. Answer B effectively showcases the interaction between ions, aligning closely with the definition of an ionic equation in a chemical context.