So that readers more easily understand a document is to show the document (cover, content, explanation) to the reader. The answer is more precisely B. By showing an example of a cover
<h2>Further explanation
</h2>
The document is an important writing that contains information.
Al Gore the author of "An Inconvenient Truth" demonstrated that the level of the carbon dioxide level in the atmosphere was getting to high and that we needed to stop polluting the air and cutting down trees of our "mother nature."
