The correct option is D Methyl lithium
Organometallic compounds are those compounds in which metal atom is directly bonded with C-atom.
Organometallic compounds contain at least one bond between a carbon atom of an organic compound and a metal. Methyl lithium has Li-C bond. In lithium methoxide and lithium acetate, Li is bonded to oxygen atom. In lithium dimethylamide, Li is bonded to N-atom. Hence, the correct answer is option (d).