Which of the following does not have a metal-carbon bond :-

An organometallic compound contains at least one direct metal-carbon bond.
$C_2H_5MgBr$ (Grignard reagent): the ethyl group is attached directly to Mg, so there is a Mg–C bond.
$K[Pt(C_2H_4)Cl_3]$ (Zeise's salt): ethylene is bonded to Pt through its $\pi$ electrons, so Pt–C bonding is present.
$Ni(CO)_4$ (nickel tetracarbonyl): each CO is bonded to Ni through carbon, so there are Ni–C bonds.
$Al(OC_2H_5)_3$ (aluminium ethoxide): each ethyl group is attached to oxygen, and oxygen is attached to Al. The linkage is Al–O–C, so there is no direct Al–C bond.
So aluminium ethoxide, $Al(OC_2H_5)_3$, does not have a metal-carbon bond.