I think the correct answer is crust. I am really sorry if I am wrong.
The Text Book title- is the correct answer
One writer was Henry Miller.
We can estimate the age of an open cluster of stars by examining (The turnoff point of the cluster)
Answer: The period known as classical antiquity began with the emergence of the city-states of ancient Greece. Later, the Roman Empire came to dominate the entire Mediterranean basin. The fall of the Roman Empire in AD 476 traditionally marks the start of the Middle Ages.
Explanation: