Henry Clay was a United States senator who redacted The Compromise of 1850.
The Compromise of 1850 was a set of five separate bills that were approved by the US Congress. The approval eased the political confrontation between Slave States and Free States on the status of the acquired territories during the Mexican–American War.
So, we can conclude that Henry Clay's speech was referring to the issue of whether the acquired states should be Slave States or Free States, claiming that the territory of The Union was only one, therefore it should be unified on these matters.
Taking this into account, we can determine that the correct answer is B: if newly added states should be Free or Slave States.