You own a stock at price S₀, and buy put options on the stock at strike price X₁, where X₁ < S₀. Further, you write call options at strike price X₂, where X₂ > S₀. You use FLEX options in the marketplace, choosing X₂ such that its call premium C(X₂) exactly equals the purchased put premium P(X₁). This trading strategy is called a .

zero cost collar

short calendar spread

butterfly spread

combination bear-bull spread

short strangle