The correct option is
B K[Pt(η2−C2H4)Cl3]Zeise's salt is a metal - alkene complex.
It is synthesized by the reaction between
K2PtCl4 and ethene, with a SnCl2 catalyst. It was one of the very first organometallic compounds to be prepared.
The anion of this air-stable, yellow, coordination complex contains a η2 - ethylene ligand.