Which of the following are rational functions? Select all that apply.
\[
\begin{array}{l}
f(x)=\frac{1}{x} \\
f(x)=\frac{x^{2}+5}{x} \\
f(x)=\frac{2^{x}}{5} \\
f(x)=\frac{x^{5}-x^{3}+4}{x^{2}+15 x-2} \\
f(x)=\frac{\log (x)}{2 x+5}
\end{array}
\]

Step 1 ：A rational function is a function that can be written as the ratio of two polynomials. The numerator and the denominator are both polynomials.

Step 2 ：Looking at the options:

Step 3 ：\(f(x)=\frac{1}{x}\) is a rational function because both the numerator and the denominator are polynomials.

Step 4 ：\(f(x)=\frac{x^{2}+5}{x}\) is a rational function because both the numerator and the denominator are polynomials.

Step 5 ：\(f(x)=\frac{2^{x}}{5}\) is not a rational function because the numerator is not a polynomial.

Step 6 ：\(f(x)=\frac{x^{5}-x^{3}+4}{x^{2}+15 x-2}\) is a rational function because both the numerator and the denominator are polynomials.

Step 7 ：\(f(x)=\frac{\log (x)}{2 x+5}\) is not a rational function because the numerator is not a polynomial.

Step 8 ：The rational functions are \(f(x)=\frac{1}{x}\), \(f(x)=\frac{x^{2}+5}{x}\), and \(f(x)=\frac{x^{5}-x^{3}+4}{x^{2}+15 x-2}\).

Step 9 ：\(\boxed{\text{The rational functions are } f(x)=\frac{1}{x}, f(x)=\frac{x^{2}+5}{x}, \text{ and } f(x)=\frac{x^{5}-x^{3}+4}{x^{2}+15 x-2}}\)