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 is 4 feet, we can calculate the circumference as follows:
\[ C = \pi \times 4 \]
Approximating \( \pi \) as 3.14:
\[ C \approx 3.14 \times 4 = 12.56 \text{ feet} \]
The best estimation from the provided options for the circumference of a circle with a diameter of 4 feet is:
13 feet.