The correct answer is option 3, Horse latitudes. Subtropical high pressure belts refer to the areas of high atmospheric pressure that exist around 30 degrees latitude in both the Northern and Southern Hemispheres. These belts are associated with calm and stable weather conditions. The term "Horse latitudes" is used to describe these regions because, historically, sailors often found themselves becalmed in this area and had to throw horses overboard to conserve water and lighten their ships. This term originated from a misunderstanding of the Spanish phrase "los caballos," which means "the horses." The other options mentioned in the question are not related to subtropical high pressure belts.