To determine the function \( g(x) \) based on the rule "rx-axis," we need to reflect the function \( f(x) = -2x + 1 \) across the x-axis.
When we reflect a function across the x-axis, we negate the entire function. Therefore, we take the negative of \( f(x) \):
\[ g(x) = -f(x) = -(-2x + 1) = 2x - 1 \]
So, the correct selection for \( g(x) \) based on the reflection across the x-axis is:
g(x) = 2x - 1