Question

What was the greatest concern of those opposing nullification during the crisis in the 1830s?

Answer 1

that states would leave the Union and gravely weaken it

Step-by-step explanation:

a). that John C. Calhoun would become president

b). that states would leave the Union and gravely weaken it

c). that the United States would fail to collect tariffs, causing a financial strain on the economy

d). that South Carolina would become much too powerful and impose slavery on other states

Answer 2

The greatest concern of those opposing nullification during the crisis in the 1830s was that South Carolina would become much too powerful and impose slavery on other states.
This was a legitimate concern as it was very bad at the time if a Southern state had so much power.