The first human remains were found in Ethiopia, which is in Africa
The American Revolution occured because the Continental Congress had borrowed money to fight the Revolutionary War and couldn't repay their debts.
The domino theory was a theory prominent from the 1950s to the 1980s that posited that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.
A domino effect or chain reaction is the cumulative effect produced when one event sets off a chain of similar events. The term is best known as a mechanical effect and is used as an analogy to a falling row of dominoes.
So the answer is the last one, “<u>It was the idea that if one nation fell to communism, others would soon follow the example</u>.”
The influence of Enlightment was expressed primarly through religion and politics. The source of enlightment ideas (like human rights, freedom etc.) are the philosophers of enlightment era (i.e. John Locke).