Explanation:

- '\documentclass{article}': This command specifies the type of document you are working on. It's standard in modern LaTeX, like LaTeX 2e.

- '\begin{document}': This command begins the content area of your document. Everything to be included in the document goes after this line, up to the end.

- '\end{document}': This command marks the end of the document’s content. It tells LaTeX to stop looking for content after this point.

- '\documentstyle{article}': This is an older command from LaTeX 2.09, which has been replaced by `\documentclass` in newer versions.

- Correct Answer: '\documentstyle{article}'