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.
Given that the diameter is 4 feet, we can substitute that into the formula:
\[ C = \pi \times 4 \]
Using the approximate value of \( \pi \) as 3.14, we can calculate:
\[ C \approx 3.14 \times 4 = 12.56 \text{ feet} \]
Thus, rounding this to the nearest whole number, the circumference is approximately 13 feet.
Therefore, the best estimation for the circumference from the given options is:
13 feet.