The formula for the circumference $C$ of a circle is given by:

$C = \pi \times d$

where $d$ is the diameter of the circle.

Given the diameter $d = 8$:

$C = \pi \times 8 = 8\pi$

Approximating $\pi$ as 3.14:

$C \approx 8 \times 3.14 = 25.12$

Thus, the closest answer is:

C. 25.13

Would you like more details or have any questions about this solution? Here are 5 questions you might consider next:

1. How do you find the area of a circle if given the radius?
2. What is the relationship between the radius and the diameter of a circle?
3. How do you convert a circumference to a diameter?
4. How does the formula for the circumference change if you use the radius instead of the diameter?
5. Can you calculate the circumference using the exact value of $\pi$ instead of the approximation?

Tip: Remember that $\pi$ is an irrational number, and its exact value is crucial for precise calculations in higher-level mathematics.