What does compression ratio measure in an internal combustion engine and why does it influence fuel choice?

What does compression ratio measure in an internal combustion engine and why does it influence fuel choice?

• A. The ratio of cylinder volume at bottom dead center to top dead center; higher ratios require higher octane fuel and can improve efficiency
• B. The ratio of engine weight to bore size
• C. The ratio of air intake to exhaust length
• D. The ratio of spark plug gap to piston stroke

Answer: (D)