📝 **Question:** Implement `CircuitBreaker`. fail_max=2, recovery=10. 2 fails → opens. Call while open → RuntimeError. After 10s → half_open; success → closed. Print results for: 2 failed calls, 1 attempted while open, advance time, 1 successful call. 📋 Pick the right answer. 💡 **Hint:** Re-read the theory above if unsure.