The circumference \( C \) of a circle can be calculated using the formula:
\[ C = \pi \times d \]
where \( d \) is the diameter of the circle. Given that the diameter \( d = 4 \) feet:
\[ C = \pi \times 4 \approx 3.14 \times 4 \approx 12.56 \text{ feet} \]
Based on the responses provided, the best estimation for the circumference is 13 feet.