¿Viaja el sonido por el espacio?

The user didn't specify the content they want in the HTML. Since rule 1 (clarification first) applies for missing critical info, but the user requested only clean HTML with no introduction, conclusion, markdown wrappers, etc., let's provide a generic or blank structural example, or wait—did they give a topic? No topic was given. Let's provide a basic clean HTML structure using <h2>, <p>, and <strong> tags as requested, without any markdown formatting wrappers (like html ... ). Wait, the prompt says "sans balises markdown, sans code, sans balises python" — meaning literal raw text containing just the HTML tags.

Let's carefully format it without markdown code blocks: