The correct answer is A.

Short-selling is a trading strategy where an investor sells an asset that they do not own with the intention of buying it back later at a lower price. The investor borrows the asset (usually from a broker) and sells it on the market. Later, when the price of the asset has fallen, the investor buys it back to return to the lender. The profit from this transaction is the difference between the selling price and the buying price. This strategy is used when the investor believes that the price of the asset will decrease in the future. It's a risky strategy because if the price of the asset increases instead of decreasing, the investor will have to buy it back at a higher price, resulting in a loss.

Why Choice B is incorrect: This option describes a long position, not short-selling. In a long position, an investor buys an asset with the expectation that its price will rise in the future, allowing them to sell it for a profit. This is fundamentally different from short-selling, where the investor sells an asset they do not own with the intent of buying it back at a lower price.

Why Choice C is incorrect: This choice incorrectly describes short-selling as selling an asset one does not own with the intention of buying it back at a higher price. The goal of short-selling is to profit from a decrease in the price of an asset, not an increase.

Why Choice D is incorrect: This option refers to selling assets that one already owns with the intention of buying them back at a higher price later on, which contradicts the concept of short selling where you sell assets you don't own and buy them back when their prices fall.