Solution: Ivan the Terrible was the Tsar of Russia from 1530 to 1585. The Byzantine calendar was the official calendar of the Russian government from 988 to 1700. The Tsar was the leader of the Russian government.
Answer: yes
Question: Did Ivan the Terrible use the Byzantine calendar?

Solution: The Tenerife Airport disaster is the deadliest crash in aviation history. The Tenerife Airport disaster involved a Boeing plane and a Pan Am plane. Pan Am airlines competed with United Airlines and other US companies. Boeing is an American multinational corporation that designs and sells airplanes, rockets, satellites,and missiles.
Answer: yes
Question: Was United Airlines blameless in worst crash in history?

Solution: Hippos are large and have large teeth. If threatened, they aggressively defend themselves.
Answer: yes
Question:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Are hippos dangerous to humans?