Octane rating methods — clarify the term: In fuel testing, the Research Octane Number (RON) refers to which of the following standardised rating definitions for motor gasoline?

Introduction / Context:
Octane ratings quantify knock resistance in spark-ignition engines. Two primary laboratory methods exist: Research (RON) and Motor (MON). Many exams test whether students can distinguish these and relate them to real-world labelling (e.g., AKI in North America).

Given Data / Assumptions:

• Standardized single-cylinder CFR engine is used.
• Research method employs milder operating conditions; Motor method uses more severe conditions.
• AKI is a separate consumer label: (RON + MON) / 2.

Concept / Approach:
RON indicates the octane rating determined under the Research method (ASTM D2699), which uses relatively mild test parameters compared with MON (ASTM D2700). It is broadly used to characterise motor gasoline and is not limited to unleaded or aviation contexts.

Step-by-Step Solution:

Verification / Alternative check:
Fuel testing manuals tabulate both RON and MON for certification; AKI appears on retail pumps in certain regions as an average of the two lab numbers.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming RON equals the number on American pumps; AKI is lower because it averages RON and MON.

Final Answer:
The octane rating measured by the Research method (ASTM D2699) under mild test conditions