Final answer:
The Abolitionist Movement, though small and consisting of a minority even within the anti-slavery movement, had a significant effect on American society and was instrumental in escalating tensions between the North and South.
Step-by-step explanation:
The movement that was small but very powerful in stimulating sectional tension between the North and the South was A) The Abolitionist Movement. During the reform period of 1820-1840, both the anti-slavery movement and the women's rights movement worked towards freedom and emancipation, with many abolitionists also being active advocates for women's rights. The abolitionist movement, led by figures such as William Lloyd Garrison and Frederick Douglass, was perhaps the most radical of the era's reform movements, insisting on immediate emancipation and highlighting the moral grievances of slavery, thus intensifying national discord.