Which one you think it is?
because i honestly don't know :/

C. 25b⁶

Step-by-step explanation:

(5b³)² = (5*b*b*b)² = (5*b*b*b)*(5*b*b*b) = 25 b*b*b*b*b*b = 25b⁶

step-by-step explanation:

circumference divided by 3.141592654 then timesthe radius twice