Hi there! I saw someone already posted the answer the question, sorry I was so late in posting this. In case you need more of an explanation, I can help with that. :)
So as you may know, , the circumference of a circle has a formula of 2(pi)radius. The radius of this circle is 4, it's half the diameter. So that would be 2(pi)(4), and, multiplying the like terms first, is 8(pi). That's 25.1327412287. But you could just write that as 8pi. That's B there. :)
Good night!