Caste is a form of social stratification characterized by endogamy, hereditary transmission of a lifestyle which often includes an occupational identity, ritual status in a hierarchy, customary social interaction, and exclusion based on cultural notions of purity and pollution.
If you're referring to Napoleon's Spanish Iberian peninsula campaign between France and the coalition of Spain, Portugal and England from 1808-1814 there were three critical reasons for its failure and one main critical importance for its failure.
The three critical reasons for its failure:
1) Napoleon greatly underestimated the fierceness and will of the Spanish fighting spirit.
2) Chiefly because of reason 1) above, the vastness of the Spanish frontier and the resources required to occupy & hold territory bled his army dry.
3) Napoleon did not expect the coalition arrayed against him to hold as strongly as it did.
The main importance of its failure was that, due to Napoleon's overly ambitious tenancy to overstretch and string-out his resources, his other armies in other theaters of war were left under strengthened.
The correct answer is:
A. Solve Italy’s economic problems.
When Benito Mussolini came into power, he promised to solve Italy’s economic problems.

The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
The factor that most promoted the spread of ideas and products from the ancient river valley civilization of Egypt and Mesopotamia to the Greek and Roman, was trade relationships.
Trade was of the utmost importance for these civilizations because it gave them the resources to live and prosper (years later, the money or currency). Through trade, not only goods were exchanged but ideas, traditions, culture, belief systems, stories, and language. One of the best examples of this is the Pantheon of gods that started with the Sumerians in Mesopotamia, which is very alike to the Pantheon of gods of Ancient Egypt, the Indus Valley Civilization, the Greek Pantheon, and the Roman Pantheon. All of them, very similar.
The United States bought the Virgin Islands from Denmark for $25 million on January 17, 1917.