To find the circumference of a circle, you can use the formula:
\[ C = \pi \times d \]
where \( C \) is the circumference and \( d \) is the diameter of the circle.
Given that the diameter \( d = 4 \) feet, we can plug this value into the formula:
\[ C = \pi \times 4 \approx 3.14 \times 4 \approx 12.56 \text{ feet} \]
The closest estimation to 12.56 feet from the options provided is:
13 feet.