What is the effect of unstable air on turbulence?

Unstable air typically leads to rough turbulence. When the atmosphere is unstable, it means that air parcels can rise and fall dramatically due to vertical temperature differences. In such conditions, warmer air at the surface can easily rise, leading to the formation of clouds and storm systems. As these air parcels move up and down, they can create chaotic and erratic air movements, which result in turbulence that can be quite bumpy and challenging for aircraft to navigate through.

In contrast, smooth air generally occurs in stable conditions where there isn't much vertical movement in the atmosphere. Steady conditions are also associated with stability, allowing for more predictable and calm flights. "Fair to Poor" would suggest variable conditions, but generally wouldn't be the direct result of turbulence caused by unstable air. Therefore, the presence of unstable air resulting in rough conditions aligns with the correct answer.