Final answer:
Both B and C are good pieces of advice for choosing an ideal race length.
Step-by-step explanation:
The correct answer is Both B and C. When choosing an ideal race length, it is advised to keep the race short enough that you will be able to complete it, as this ensures that you can successfully finish the race without feeling overly fatigued. At the same time, it is also recommended to make the race long enough to be challenging, which allows you to push yourself and improve your endurance. So, it is important to strike a balance between the two aspects.
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