Which type of fog is produced when air is lifted over a topographic barrier?

Upslope fog forms specifically when moist air is lifted over a topographic barrier, such as a mountain or hill. As the air ascends, it cools due to the decrease in pressure and temperature at higher altitudes, causing the moisture in the air to condense and form fog. This process is closely related to orographic lifting, where geographical features force the air to rise, leading to saturation and cloud formation.

In contrast, radiation fog typically develops on clear nights when the ground loses heat quickly, cooling the air directly above it to the dew point. Advection fog occurs when warm, moist air moves over a cooler surface, causing the air to cool and condense into fog. Valley fog forms in low-lying areas, where cool air settles overnight but is primarily a result of radiative cooling rather than uplift over a barrier.

The unique mechanism of lifting moist air over terrain is what specifically characterizes upslope fog, making it the correct answer to the question.