Final answer:
A secondary depression commonly forms ahead or near the top of a primary depression, as it is a disturbance created by the primary depression itself.
Step-by-step explanation:
The question regarding where a secondary depression is most likely to appear considering a primary depression is related to meteorology, which falls under the subject of Geography. A secondary depression, also known as a secondary low, typically forms near the top or ahead of the primary depression. This is because the primary depression can create a trailing disturbance in the atmosphere that can lead to the development of an additional area of low pressure. Secondary depressions can enhance the wind and precipitation patterns of the primary depression, making weather conditions more severe.