Which type of air continues to rise of its own accord once lifted?

The correct choice, unstable air, refers to air that, when lifted, has a tendency to continue rising on its own. This phenomenon occurs because unstable air is characterized by a lower density than the surrounding environment at higher altitudes. When a parcel of air is heated (often from the ground or other sources) and becomes warmer than the surrounding air, it rises due to buoyancy. This upward movement continues until the air reaches a point where it either becomes cool enough to stop rising or is displaced by other atmospheric conditions.

Unstable air is typically associated with conditions conducive to convection, turbulence, and the formation of clouds, including cumulonimbus clouds, which can lead to severe weather. This contrasts with stable air, which resists vertical movement and tends to spread out horizontally, leading to calm conditions and clear skies. Cold air does not inherently rise; in fact, it tends to sink due to its density, and dense air also tends to remain at lower altitudes rather than rising.