In what two ways do scientist think prehistoric people reached the Americas?

All i need is an outline i need with getting started with a research paper. i need with an outline for history of slavery. i don’t know how i should start it end. i need with an outline.

List three reasons why explorers began to explore new, and old areas. [[ps: doesn't explicitly say where. i think it's more in general.

What impact did entry into ww1 have on life in the us?