What was the “root issue” that prevented Congress from adding Texas to the U.S. for many years?

Question

B the issue of slavery
C a treaty with Mexico
D the Monroe Doctrine

Answer 1

The "root issue" that prevented Congress from adding Texas to the U.S. for many years was B. the issue of slavery. The annexation of Texas was contentious partly because it would have introduced a large territory that allowed slavery into the Union, raising the political tensions between free and slave states.