A short sale requires the customer to borrow shares because the customer is selling securities not currently owned. The SIE trading framework classifies this under short positions, margin activity, and trading mechanics. The borrowed shares are not subject to a fixed five-business-day or seven-business-day return deadline merely because they were borrowed for a short sale. Instead, the short position can remain open as long as the broker-dealer can maintain the stock loan and margin requirements are satisfied. However, the lender or broker-dealer may recall the borrowed stock, requiring the customer to cover the short position by purchasing equivalent shares in the market. This is why choice C is correct. Choice D is incorrect because the broker-dealer’s right to recall the borrowed securities is not dependent on whether the customer has realized a profit. The official SIE outline specifically includes “Long and short, naked and covered” under Orders and Strategies, and margin- related customer account rules under trading and account compliance. Reference: Section 3.1.1 Orders and Strategies; Section 3.2.1 Account Types and Characteristics; FINRA Rule 4210 Margin Requirements.