To solve this problem you must apply the proccedure shown below:
1. You have the following information given in the problem above:
The angle is: 90 degrees
radius=6 m
2. 90 degrees is radians:
90°xπ/180°=π/2
3. Therefore, you have the length of the arc is:
=(6 m)(π/2)
=3π
Therefore, the answer is the option C. C. 3π