Petroleum fuels and test methods: pick the single correct statement from the following about octane, smoke point, kerosene evaluation, and aviation fuel properties.

Introduction:
This question checks core petroleum property knowledge: the influence of hydrocarbon structure on octane and smoke point, how kerosene suitability as an illuminant is evaluated, and which low-temperature properties matter for aviation fuels. Selecting the correct statement requires recalling which test or property applies to which product and why.

Given Data / Assumptions:

• Paraffins vs iso-paraffins: branching generally raises octane.
• Aromatics typically have poor smoke point compared with paraffins.
• Kerosene suitability for burning/illumination can be gauged by smoke point and char value tests.
• Aviation fuels require low freezing point and low cloud point for cold-altitude operation.

Concept / Approach:
Evaluate each statement against standard refinery and fuel-testing principles. Branching improves gasoline octane; thus normal paraffins do not exceed iso-paraffins in octane. Aromatics have higher sooting tendencies and therefore lower smoke points than paraffins. Kerosene's performance as an illuminant historically uses smoke point and char value measurements. Aviation fuels must avoid waxing at altitude, so they target low (not high) cloud and freezing points.

Step-by-Step Solution:
Check option a: incorrect because iso-paraffins have higher octane than normal paraffins of the same carbon number.Check option b: incorrect; aromatics yield lower smoke points than paraffins.Check option c: correct; char value (with smoke point) is used to judge kerosene suitability for illumination/burning quality.Check option d: incorrect; aviation fuels require a low cloud point/freezing point.Check option e: incorrect; octane strongly increases with branching.

Verification / Alternative check:
Fuel property tables consistently show iso-paraffins > n-paraffins in octane; smoke point is degraded by aromatics; kerosene tests include smoke point and char value; jet fuel specifications emphasize low freeze/cloud points.

Why Other Options Are Wrong:
a: Reverses the well-known octane trend.b: Opposite of smoke point behavior; aromatics smoke more.d: Aviation needs low-temperature flow properties; cloud point must be low.e: Branching clearly affects octane.

Common Pitfalls:
Mistaking diesel/kerosene smoke point behavior for gasoline octane behavior; confusing cloud point requirements for aviation with diesel cold-flow specs.

Final Answer:
Suitability of kerosene as a fuel and as an illuminant may be assessed using the char value test.