The ends of the geologic eras such as the paleozoic and mesozoic are marked by
a.
mass extinctions.
b.
index fossils.
c.
radioactive decay.
d.
climate changes.

Write two paragraphs to explain how the cold war changed after the 1960s. first, identify the ways it changed during leonid brezhnev's leadership in the 1970s. then, explain how the cold war changed when ronald reagan was in office in the early 1980s. include supporting facts and details from the text in your response.

What religion influenced the first persian empire as established by cuyrus the great?

How did people in the 14th century understand black death