What is the biggest difference between an option and a futures contract?

Select one: a. Options give the right to buy or sell while a futures contract is an obligation and commitment to buy or sell. b. Options are traded on exchanges while futures are not. c. Options give investors a way to manage portfolio risk while futures do not. d. Options can be used by speculators to profit from price fluctuations while futures cannot. e. Options contracts are contractual agreements whereas futures contracts are not.