The correct answer is option 2: Sub-tropical high pressure belt.

Horse latitudes are regions found at around 30 degrees latitude in both the northern and southern hemispheres. These regions are characterized by high atmospheric pressure, which is caused by the descending air masses from the tropics moving towards the poles.

In the Sub-tropical high pressure belt, air masses descend from higher altitudes and create a stable atmospheric condition. This stable condition prevents air from rising, resulting in minimal cloud formation and generally calm weather. As a result, these regions tend to have clear skies and relatively light winds, which are ideal for sailing. The name "Horse Latitudes" originated from the era of sailing ships, when sailors would sometimes have to throw horses overboard due to the lack of wind, leading to a legend that ships crossing this region would get stuck.

To summarize, Horse Latitudes are found in the Sub-tropical high pressure belt, characterized by high atmospheric pressure, clear skies, and calm winds.