In the 1820s, the united states was concerned about european ambitions in the americas because they feared that europe wanted to

The correct answer is B. Conquer new Latin American republics. 
In the 1810s, a series of revolutions broke out in Latin America, resulting in nearly all of Latin America being independent by the end of the 1820s. These new republics could be conquered by European nations, and Russia had expressed their desire to expand down the Pacific Coast. I hope this has helped!