In what manner do spoilers affect an aircraft during descent?

Spoilers are devices used on aircraft wings that serve to disrupt airflow over the wing's surface. When deployed during descent, spoilers create turbulence and reduce the lift produced by the wing. This intentional disruption is useful for decreasing altitude and increasing descent rate without gaining excess speed.

By interrupting the smooth airflow over the wing, spoilers effectively reduce both lift and drag, allowing the aircraft to descend more quickly. This is crucial because it provides pilots with control over descent profiles, particularly during landing approaches. Thus, answer B accurately describes the primary function of spoilers in influencing the aircraft's behavior during descent.

Other answer choices do not correctly depict the role of spoilers. For instance, increasing lift and decreasing drag contradicts the primary function of spoilers, as they are designed to reduce lift. Gaining altitude is not a function of spoilers; rather, they help in descending. Improve engine performance is unrelated to the effects of spoilers, which specifically affect aerodynamic characteristics rather than directly influencing engine function.