Final answer:
The best way to correct the sentence is option A: Included flexibility exercises as part of the warm up and cool down.
Step-by-step explanation:
The best way to correct the sentence is option A: Included flexibility exercises as part of the warm up and cool down. This option provides a clear and grammatically correct way of including flexibility exercises. Option B contains a comma splice and should be avoided. Option C is not a complete sentence, and option D introduces a different subject and doesn't provide a correction for the sentence.
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