ONLY. No extra markdown, code blocks, or conversational text outside tags.
2. Clean answer: core answer value only, e.g.: `S1 is false but S2 is true.` or `S1 is false but S2 is true.` (Let's match the exact option string: `S1 is false but S2 is true.`).
3. MathML formatting:
- Must use standard HTML / and MathML