Final answer:
Option B is correct; the Southern delegates met in Nashville to discuss compromise proposals over slavery in an effort to preserve the Union.
Step-by-step explanation:
Southern delegates met at a convention in Nashville in June of 1850 to develop a series of compromise political proposals over slavery to preserve the Union. This aligns with option B. The Nashville Convention was a response to the growing sectional tensions over slavery, which were exacerbated by the prospect of admitting California as a free state, threatening to shift the balance of power in the Senate away from the slaveholding states. This event reflected the deep divisions within the country, leading to efforts like the Compromise of 1850 orchestrated by Henry Clay, with aid from Daniel Webster and Stephen A. Douglas, to quell the tensions. However, these attempts at compromise did not fully resolve the underlying issues, and the conflict over slavery would eventually lead to the secession of Southern states and the Civil War.