Which of the following factors best explains the territorial expansion of slavery in the middle of the nineteenth century?

The expansion of US territories

Explanation:

Jefferson's acquisition of the Louisiana territories in 1803 doubled the size of the US coupled with the victory in the Mexican-American War extending the U.S territories to the Pacific which further tripled its area. This expansion invariably led to the spread of slavery.

The Mexican american war incorporated extensive new lands into the United States.

i believe it d) heterogeneous

explanation:

nutelal