The correct answer is D) the belief in Manifested Destiny meant that the balance between free and slave states could shift as the United States expanded to the Pacific Coast.
In the early 1800s, the belief in Manifest Destiny was most likely to affect the admission of new States into the Union in that " the belief in Manifested Destiny meant that the balance between free and slave states could shift as the United States expanded to the Pacific Coast."
Manifested Destiny was the belief that the US was destined to conquer and expand its territories. After the Louisiana purchase of 1803, President Thomas Jefferson ordered the Lewis and Clark Expedition to explore the newly acquired territories and start a westward expansion. Politically, Manifested Destiny implied a balance between free and slave states and a shift in power in the US Congress.
The other options of the question were A) the belief in Manifested Destiny meant that slavery was likely to spread to all the territories as they became new states. B) the belief in Manifested Destiny meant that European nations were likely to give up their claims to territories to avoid a battle on slavery. C) the belief in Manifested Destiny meant that the US was destined to outlaw slavery in every state.