$\"\"$

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Observe the figure:

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The radius of the circle is $\"\"$ .

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Find the arc length of $\"\"$ .

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The arc length of $\"\"$ .

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Substitute $\"\"$ and $\"\"$ .

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Arc length of $\"\"$ .

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Therefore, the correct choice is option $\"\"$ .

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$\"\"$

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The correct choice is option $\"\"$ .