Concept:Identify the longest continuous carbon chain and number it from the end nearest the substituent.Explanation:The longest continuous chain contains four carbon atoms, so the parent alkane is butane.A methyl substituent (−CH3) is attached to carbon number 2.Number the chain so that the substituent gets the lowest possible locant, giving 2-methylbutane.There is no need to include the prefix "1-" for a methyl group on a five-carbon chain because the parent chain is correctly chosen as butane.Answer:The correct IUPAC name is 2-methylbutane, option C.
