A synthetic commodity position for a period of T years can be constructed by entering into a long futures contract with T years to expiration and buying a zero-coupon bond expiring in T years with a face value of the present value of the futures price. The payoff function at time T is as follows:

• Payoff from long futures position = $S_T - F_{0,T}$, where $S_T$ is the spot price of the commodity at time T and $F_{0,T}$ is the current futures price.
• Payoff from zero coupon bond = $F_{0,T}$

Hence, the total payoff function equals $(S_T - F_{0,T}) + F_{0,T}$ or $S_T$. This creates a synthetic commodity position.

Option A is correct because it involves buying the forward contract and buying the zero-coupon bond, which aligns with the method to create a synthetic long position in commodity X for a period of 6 months. Options B, C, and D are incorrect as they do not match the strategy described for creating a synthetic commodity position.