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Stop generation immediately after outputing the Final Answer.

Ensure that your response strictly follows the format to maintain clarity and consistency. 
Question: Here are some premises:
Some professional basketball players are not American nationals.
All professional basketball players can do jump shots.
If someone can jump shots, they leap straight into the air.
If someone leaps straight into the air, they activate their leg muscles. 
Yuri does not activate his leg muscles.
Here is a conclusion:
Yuri is an American national.
Based on the premises, is the conclusion True, False, or Uncertain?
Answer: Uncertain