The formula to calculate the circumference \( C \) of a circle is given by:
\[ C = 2\pi r \]
where \( r \) is the radius of the circle. Given that the radius \( r \) is 2.5 feet and using \( \pi \approx 3.14 \):
\[ C = 2 \times 3.14 \times 2.5 \]
Calculating it step by step:
- Calculate \( 2 \times 2.5 = 5 \).
- Now calculate \( 5 \times 3.14 = 15.7 \).
Thus, the estimated circumference is:
\[ C \approx 15.7 \text{ feet} \]
So, the correct response is 15.7 feet.