The cetane number of a Diesel fuel is a measure of

Solution (By Examveda Team)

The correct answer is (C) Ignition quality.

Let's break down why:

* Cetane Number: This is a special rating for diesel fuel, just like octane rating is for gasoline.

* Ignition Quality: It tells us how easily and quickly the diesel fuel will start burning (ignite) when it's injected into the hot, compressed air inside a diesel engine.

* Higher Cetane Number: Means the fuel ignites more readily and smoothly, leading to easier starting, less engine knocking, and reduced emissions.

Now let's look at why the other options are not the best fit:

* (A) Volatility: Volatility refers to how easily a liquid turns into a vapor. It's more closely related to gasoline properties (measured by vapor pressure) than diesel fuel's ignition behavior.

* (B) Viscosity: Viscosity is a measure of a fluid's resistance to flow (its thickness). While important for diesel fuel, it's not directly related to the fuel's ignition characteristics.

* (D) Delay Period: The delay period is the time between when the diesel fuel is injected and when it starts to burn. The cetane number is *related to* the delay period (a higher cetane number means a *shorter* delay period), but the cetane number *directly measures* the ignition quality, not the delay period itself. Ignition quality is the broader concept.

Therefore, Cetane number is the measure of Ignition Quality.