A mixture of 45%cetane and 55% alpha-methyl-naphthalene is f...

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______.A.cetane number of 55B.cetane number of 45C.octane number of 55D.octane number of 45请帮忙给出正确答案和分析，谢谢！