Byzantium/Constantinople was conquered in 1451, but the empire continued to decline starting around the 18th or 19th centuries. It officially died in WWI. As for how long it was a major threat to Europe, the empire's prime was the 16th century, under Suleiman the Magnificent.
Answer:
the answer is...
Explanation:
1. A women ran for and is the vice president
2. Joe Biden is the oldest presidential candidate to run for and be in office
3. Because of the pandemic, mail in ballots were used; which has never happened before