These can be some shared characteristics by civilizations:
Big population centers: These help people survive with the
help of each other, like farmers can grow and sell in these areas etc.
Monumental Architecture or Art: This will be identified as
their legacy
Record Keeping: This can be a language or any other recording
system to help record the history and traditions.
System of administering areas: Help run the place smoothly.
Labor division: Various people are skilled at various jobs,
to do a certain job a skilled laborer is required.
Social Class System: It can be based on wealth as well as
the type of work performed.
Answer:
The US government's decision to develop a hydrogen bomb, first tested in 1952, committed the United States to an ever-escalating arms race with the Soviet Union. The arms race led many Americans to fear that nuclear war could happen at any time, and the US government urged citizens to prepare to survive an atomic bomb. Their reason for this panicked prognosis was the United States' decision to develop and test a hydrogen bomb, or H-bomb, a nuclear weapon one thousand times more powerful than the atomic bomb that had leveled Hiroshima at the end of World War II.
Explanation:
The arrival on the Europeans
It was a safety net against poverty for people over the age of 65, as well as being a welfare system for disabled people.