What will insert an exclamation point after every h2 element?

The correct choice utilizes the ::after pseudo-element, which is specifically designed to insert content after an element's content. By using h2::after { content: "!"; }, the CSS rule effectively adds an exclamation point directly after every <h2> element in the HTML. The content property is crucial here, as it specifies what will be displayed; in this case, it's the exclamation point.

The other options do not fulfill the requirement to properly insert content after the <h2> elements. The use of :before in one option would place the exclamation point before the <h2> content instead of after it. Additionally, using value rather than content is incorrect because the value property does not exist for pseudo-elements in this context; it should always be content to define what text or symbol is displayed. As such, the only valid and functional option for inserting an exclamation point after each <h2> is the one that correctly employs the ::after pseudo-element with the content property.