An unrealized gain occurs when the value of an asset increases but has not yet been sold. If the customer sells the stock, the unrealized gain becomes a realized gain.

B is correct because the increase in value without selling the stock is an unrealized gain.

A is incorrect because interest income refers to earnings from fixed-income securities.

C is incorrect because operating profit relates to a company’s earnings, not an investor’s portfolio.

D is incorrect because " out of the money " is a term used for options, not stocks.