It is A but there was also 5 main causes of imperialism
1. Political (nationalism, to be the most powerful country by ruling many other countries).
2. Economical (to use other country's resources, recieve cheap labor, have a market for their goods. i.e. Africa).
3. Religious (to spread their religion. i.e. missionaries)
4. Idealogical (believed that their race was better and had to civilize other people by teaching them. i.e. The White Man's burden)
5. Exploratory (people wanted to explore new lands for mapping, etc.)