Step 1: Differentiating the function.
We are given that \( y = e^x \). The first derivative is:
\[
\frac{dy}{dx} = e^x
\]
Step 2: Finding the second derivative.
Differentiating again, we get:
\[
\frac{d^2y}{dx^2} = e^x
\]
Step 3: Conclusion.
Thus, the second derivative of \( y = e^x \) is \( e^x \), corresponding to option (a).