Which statement is true regarding spins?

A spin is a specific aerodynamic condition that occurs when an aircraft is stalled and loses controlled flight. The characteristic of a spin is that both wings are indeed stalled. This means that neither wing is producing sufficient lift to recover from the spin, which results in a rotation around the aircraft's vertical axis. During a spin, the aircraft typically enters a descending spiral, and the stalled condition of both wings maintains this rotation.

In contrast to the correct statement, if only one wing were stalled (as suggested by one of the incorrect options), the airplane would typically not enter a spin; rather, it might experience a condition where one wing is generating more lift than the other, leading to a roll but not a spin. The reference to level flight in another option also misrepresents the nature of a spin, as a spin is not synonymous with level flight but rather a demonstration of an aircraft in a lost control situation, characterized by the combination of rotations and descent.

Ultimately, spins are fundamentally about both wings exceeding their critical angle of attack, resulting in a stall and the accompanying rotational behavior. Understanding the dynamics of spins is crucial for pilots to recognize and recover from potential situations leading to a spin.