The correct answer is A. When California applied for statehood, the Southern states feared that they would lose equality in the Senate. Before the admission of California, Southern slavist states and Northern free states had the same number of Senators. But when California was admitted in 1850, it entered into the Union as a free state, so it created a power disbalance for the Southern states, giving to extra votes to the abolitionist states.
The whole states were Arkansas, Iowa, Missouri, Kansas, Oklahoma, and Nebraska. There are many more parts of states that came with the purchase and if you need more information google it :)
It was located in the middle of the major crossroads.
The answer is B.
I hope I helped and please mark brainilest when u get the chance :)