The correct answer is: B. Surreptitious
Surreptitious means done in a secret or stealthy way. It is often used to describe actions that are illegal or unethical. For example, a person might steal something in a surreptitious manner.
Hidden means not seen or not easily seen. It can be used to describe things that are physically hidden, such as a secret compartment in a piece of furniture, or things that are not easily understood, such as a complex mathematical equation.
Obscure means not well-known or not well-understood. It can be used to describe things that are not well-known to the general public, such as a little-known fact about history, or things that are not well-understood by experts, such as a complex scientific theory.
Exposed means not covered or hidden. It can be used to describe things that are physically exposed, such as a person’s skin when they are not wearing clothes, or things that are not hidden from view, such as a secret that has been revealed.
In the context of the question, “underhand” means done in a secret or dishonest way. The answer that best matches this definition is “surreptitious.”