Matias's position is a short futures position. In a futures contract, the investor agrees to sell the underlying asset at a predetermined price on a specific future date. In this case, Matias has agreed to sell 5,000 troy ounces of gold in April, which is a classic example of a short futures position. This position allows Matias to profit if the price of gold falls before the delivery date in April. It's important to note that futures contracts are standardized and traded on exchanges, which provides liquidity and reduces counterparty risk. However, it also exposes the investor to the risk of adverse price movements.

Choice A is incorrect. A hedged futures position involves taking a long and short position in two different but related markets to reduce risk. Matias only has a single open position on gold futures contracts, which does not constitute a hedged futures position.

Choice B is incorrect. A short put option position would mean that Matias has sold the right to another party to sell him gold at a predetermined price before the contract expires. However, as per the question, Matias is required to sell gold in future which aligns with the definition of a short futures contract rather than a put option.

Choice D is incorrect. While both forwards and futures contracts involve an agreement to buy or sell an asset at a future date, they differ in key aspects. Forwards are customized OTC contracts, while futures are standardized contracts traded on exchanges. The question specifies that the contract is on the London Exchange, which suggests it is a futures contract rather than a forward contract.