A mixture of 45% cetane and 55% alpha-methyl-naphthalene is found to have the same ignition delay as a sample of diesel oil. The sample can be described as having a/an __________.

Correct Answer: Option B — cetane number of 45

Cetane number is defined by the volumetric percentage of pure cetane in a reference fuel blend matching the ignition delay of the test fuel, making a 45% blend equal to a cetane rating of 45.