Answer:
b. the US needed to secure its political and trade interest.
Step-by-step explanation:
The main reason why the United States wanted to engage in imperialism in the 1800s was because it wanted to protect its political and trade interests. The United States believed that the best way to ensure that its interests were protected was by establishing colonies in strategic regions. This would provide the country with more power and resources, as well as a larger number of trading partners.