Call it a pre-Christmas lottery ticket, but someone in the oil market has been busy making a bold bet, buying contracts that will be profitable if oil surges again to $100 a barrel. The $100 December 2018 call option — a contract that gives the right to buy Dec. 2018 futures at $100 per barrel — was the most traded contract on Tuesday across the whole ICE Brent market, the latest sign of resurgent optimism in oil.