<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.
Answer: ...have obtained independence during post-war period (during 1950s, 1960s and 1970s).
Explanation: we have to include Dutch (Surinam for example), French (Algeria or Vietnam), Belgian (Kongo-Kinshassa) or Portuguese (Angola, Mozambique) colonies. This process included return of white-Europeans colonists back to Europe: the biggest return was that of Algerian French (Pieds-Noirs) and later (not so big) European whites from Portuguese territories (1974-1975-1976).
I looked all over the Internet, and saw that there is another option that you didn't include, and which is actually the correct answer.
Bays best facilitate the building of ports, not these options.
I believe that would be Mesopotamia, the seat of the Sumerian and Akkadian civilizations.
Source: Studied this last week. :)