To reflect the function \( f(x) = (x+1)^2 \) over the x-axis, you need to take the negative of the entire function.
The reflection is given by:
\[ g(x) = -f(x) \]
Substituting \( f(x) \):
\[ g(x) = - \left( (x+1)^2 \right) \]
This simplifies to:
\[ g(x) = - (x+1)^2 \]
Thus, the correct answer is:
d. \( g(x) = - (x+1)^2 \).