The best method of preparation of an alkane with odd number of carbons from two alkylhalides is (a) Wurtz reaction (b) Kolbe's electrolysis (c) Corey-House synthesis (d) Ullmann reaction

Before finding the best method, we need to understand each of the four given methods: (a) Wurtz reaction: A coupling reaction where two alkylhalides react in the presence of sodium metal to form a symmetrical alkane with an even number of carbons. (b) Kolbe's electrolysis: An electrochemical decarboxylation reaction involving the conversion of a carboxylic acid (or its salts) into an alkane, usually with an even number of carbons. (c) Corey-House synthesis: A two-step reaction involving organocuprates to form new carbon-carbon bonds, allowing the preparation of both symmetric and asymmetric alkanes. (d) Ullmann reaction: A copper-catalyzed coupling reaction involving the reaction between an aryl halide and an amine to form a biaryl compound.

Comparing these methods: - The Wurtz reaction and Kolbe's electrolysis generally yield alkanes with an even number of carbons, which does not fulfill our requirement. - The Ullmann reaction yields biaryl compounds and not alkanes, so it is not suitable for the given condition. However, the Corey-House synthesis has the flexibility to create both symmetric and asymmetric alkanes, which means it can be used to prepare an alkane with an odd number of carbons.

Based on the analysis above, the best method of preparation of an alkane with an odd number of carbons from two alkylhalides is: (c) Corey-House synthesis