Correct option is D
Grubbs catalysts are a series of transition metal carbene complexes used as catalysts for olefin metathesis. Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds.
Grubbs reported the second-generation catalyst, based on a saturated N-heterocyclic carbene (1,3-bis(2,4,6-trimethylphenyl) dihydroimidazole):







