A synthetic call option can be created by taking a long position in a stock, a long position in a put option, and a short position in a zero-coupon bond. This combination of positions replicates the payoff of a long position in a call option. The underlying principle behind this strategy is the put-call parity, which is a fundamental concept in options pricing. The put-call parity states that the price of a call option (c) plus the present value of the strike price (X) discounted at the risk-free rate (r) for the time to maturity (T) is equal to the price of the stock (S) plus the price of a put option (p). Mathematically, this is represented as $c + X(1+r)^{-T} = S + p$. Rearranging this equation to solve for the price of a call option, we get $c = S + p - X(1+r)^{-T}$. This equation shows that a call option can be synthetically created by taking a long position in a stock, a long position in a put option, and a short position in a zero-coupon bond. This strategy allows an investor to replicate the payoff of a call option without actually owning the option.\n\nChoice A is incorrect. While a long position in a stock and shorting a put option can replicate the payoff of a call option, shorting a zero-coupon bond would not contribute to this synthetic strategy. Shorting the bond would create an obligation to pay at maturity, which is not characteristic of a call option's payoff.\n\nChoice B is incorrect. This choice involves both long and short positions in options (call and put respectively), which does not replicate the payoff of just one call option. Additionally, shorting a zero-coupon bond again introduces an obligation that does not align with the desired payoff.\n\nChoice C is incorrect. Shorting a stock and going long on both put options and zero-coupon bonds do not mimic the characteristics of being long on call options. In fact, this combination could potentially lead to unlimited losses if the stock price increases significantly – something that doesn't happen when holding only call options.