15. A firm planning to sell oil might anticipate a period of market volatility and wish to protect its revenue against price fluctuations. To hedge the total revenue from the sale, the firm: A. enters a long position in oil futures or purchase a call option on oil. B. enters a long position in oil futures of purchases a put option on oil. c. enters a short position in oil futures or purchase a call option on oil. D. enters a short position in oil futures or purchases a put option on oil