The correct response is:
The a-value is negative because the graph is of a parabola that opens down.
This is because a parabola that opens downward has a negative a-value in its quadratic equation \(y = ax^2 + bx + c\). Conversely, a parabola that opens upward has a positive a-value. The orientation of the parabola is determined by the sign of the a-value.