Answer:
it's e and c I think at least hope this helps.
The correct answer is c. they used darker, bolder colors in the distance
This gives of the impression of 3D even though it's not really there since it seems like the darker places are further away and are therefore darker since they can't be seen clearly.
I will check/see your book.
i think 1846 cuz thats when they separated the countires and when the united states was about to contain land access, but im not 100% on that answer i just skimmed threw the paragraph
