Which of the following indicates potential fog formation?

A small temperature/dew point spread indicates potential fog formation because it signifies that the air is nearly saturated with moisture. Fog commonly forms when the temperature drops to near the dew point, causing water vapor in the air to condense into tiny liquid water droplets. When the temperature and dew point are close to each other, the likelihood of saturation increases, especially during calm and clear nights when the air cools down.

In contrast, a large temperature/dew point spread suggests that the air is dry, which reduces the chances of condensation and, consequently, fog formation. Strong winds can mix the air, which typically disperses moisture and helps prevent fog. Low humidity levels indicate that the air is not holding much moisture, again making fog less likely.