Final answer:
The soil type most likely to be found in mountainous or sandy regions is Aridisols. These soils are associated with dry, arid environments typical of deserts and are characterized by limited moisture, which is suitable for such regions.
Step-by-step explanation:
Aridisols are typically found in arid environments, where there is limited moisture for the formation of more developed soil profiles. These soils are common in desert areas, which align with the question's description of mountainous or sandy regions that often have similar dry conditions.
Alfisols are more fertile and are often associated with temperate forests, not arid or sandy regions. Andisols develop from volcanic ash and are found near volcanoes, which might not necessarily correlate with the generic 'mountainous or sandy regions' described in the question. Ultisols, on the other hand, are found in more humid, subtropical areas. Therefore, based on the characteristics of these soil types, Aridisols are the correct answer for areas described as 'mountainous or sandy' typically referring to type B: Dry or arid climates found in desert-like environments.