A customer has a stock position that has increased in value since the time he...

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.