Correct option is (c) Mg
Easy explanation: various liquids as solvents, preferably organic acids relatively inert to oxidation; catalysts such as salts of Ce, Co, Cu, Mn, V, U, Fe; plus promoters such as salts of Ba, Mg, Ki plus “initiators” such as peroxides, peracids, aldehydes, ketones, olefins, or organic substances forming peroxides.