Lifting weights is safe for kids, provided they are mature enough to follow instructions and use proper technique
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Between 20% – 30% of the school.
Explanation:
The best answer for the blood vessels' valves would be these are veins that would then help in preventing the back flow of blood because the walls have small muscle to pump the blood back to the heart.Hope this is the answer.
False, crossover designs are not most useful when the underlying intensity of disease has substantial within-person variability, such as larger seasonal changes.
<h3>When is crossover designs most useful?</h3>
A crossover design is a repeated measurements design such that each experimental unit receives different treatments during the different time periods.
That is the patients cross over from one treatment to another during the course of the trial.
Thus, crossover designs are not most useful when the underlying intensity of disease has substantial within-person variability, such as larger seasonal changes.
Learn more about crossover designs here: brainly.com/question/28039233
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