The firing order of eight-cylinder engine is

• A. 1 ? 5 ? 4 ? 2 ? 6 ? 3 ? 7 ? 8
• B. 1?2?6?3?4?7?5?8
• C. 1?5?3?4?2?7?8
• D. 1?2?4?6?7?3?5?8