Wo ist das größte Straßenbahnnetz der Welt?

The user's prompt is a request to return only clean HTML code (h2/p/strong) without any introduction, conclusion, markdown, or extra wrappers, but they haven't specified what content to put into HTML.

Wait, let's look at the instructions. The user prompt says: "Retourne uniquement le code HTML propre (h2/p/strong), sans introduction, sans conclusion, sans balises markdown, sans code, sans balises python." (Return only clean HTML code, without intro, conclusion, markdown, code, or python tags).

Since no topic or content was provided by the user, what should I put? Or is it a generic prompt? Let's check if there's any sensitive content or if it's completely safe. It's completely safe (just asking for HTML). But since no subject is provided, I should provide a basic structure or a helpful placeholder, or maybe a simple message formatted in HTML as requested. Wait, let's keep it minimal and compliant with the formatting constraints (no markdown code blocks, just raw HTML).

Let's check the rules:

• Flat structure, no root wrapper tag if possible, or just raw HTML elements.

• No markdown code fences since the user said "sans balises markdown, sans code".

Let's output simple HTML tags directly: