Which of the Following Best Defines a Real Option

Which of the following best defines a real option?

A) The lower bound of an option's value, or what the option would be worth if it were about to expire.
B) A contract that gives its owner the right to buy or sell some asset at a fixed price on or before a given date.
C) The value of a convertible bond if it could not be converted into common stock.
D) The right to sell an asset at a fixed price during a particular period of time. The opposite of a call option.
E) An option with payoffs in real goods.