Answer:
D. Manifest Destiny.
Explanation:
The idea that the U.S. was meant to expand into new territories was known as Manifest Destiny.
This was very important during Westward Expansion and at the end of the 1800s, many Americans thought the U.S. should continue to expand, even overseas.
There are hardly any
It's mostly side effects such as mild fevers and stuff, but vaccines are a must
