They warm up to get the blood into their muscles , it is not the joints that need warming. Increased blood flow may reduce injury and improve performance. If you are only asking what a flexible joint is that would be one that can move through its range of motion so the movement of a limb is not restricted. Hope this helps!
ANSWER:
a) matches 3
b) matches 1
c) matches 2
~batmans wife dun dun dun...aka ~serenitybella
Answer:
Iris
Explanation:
The iris opens and closes to control the amount of light entering through the pupil (schepens.harvard.edu).