A long straddle

a. consists of selling and writing an equal number of puts and calls with different strike prices but the same expiration date and the same underlying security.

b. is a strategy based on the expectation that the price of the underlying security will be relatively constant.

c. consists of buying a call at one strike price and then writing a call at a higher strike price.

d. is a strategy that produces profits when the price of the underlying security moves significantly in either direction.