Which of the following compounds cannot be prepared by the Wurtz reaction.?

When two moles of alkyl halide on treatment with dry sodium metal in presence of dry ether solvent to form alkane is called Wurtz reaction.Limitation It is not a good method for the preparation of asymmetric alkane.Since in order to prepare asymmetric alkane we need to mix two different alkyl halides,then it gives mixture of three different alkanes and their seperation is highly difficult.