Which one of the following is not a product of Wurtz reaction?

where  by two alkyl halides are reacted with sodium metal in dry ether solution to form a higher alkane: 

               2R-X+2Na→R-R+2Na⁺X 

Unsymmetrical alkanes may also form by Wurtz reaction, though the product mixture will have a mixture of products and hence, Wurtz reaction is generally not preferred for forming unsymmetrical alkanes.

 R-X + Na +R'-X →R-R +R'-R '  +R-R'+ 2Na⁺  X Since the reaction is a coupling reaction, at least 2 Carbons will be present in the product and hence, Methane cannot be formed by this reaction even in small quantities.