Answer:
A, They mapped the land and reached the Pacific Ocean, helping the US set claim.
Add-on:
I hope this helped at all. I'm sorry if its incorrect.
Your answer to this question Plateau
<u>B - A theory that stated if Vietnam fell to communism the rest of the region would soon follow.</u>
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People were afraid that once Vietnam fell into communism that surrounded places would soon follow. Vietnam would be the first domino to fall and hit the rest of the region causes more communism.
