In the Quadratic Regression Model Y = β₀ + β₁X₁

In the quadratic regression model y = β₀ + β₁X₁ + β₂X₁² + ε, the β₁ term represents the

A) rate of curvature of the parabola.
B) value of Y when X is zero.
C) shift parameter of the parabola.
D) y-intercept of the parabola.