On a parabola, the extreme point (which is the highest, lowest, or farthest point left or right) is called the _____.A.centerB.directrixC.focusD.vertex

The extreme point on a parabola is called the vertex.

Explanation:

1. Vertex Definition: The vertex of a parabola is the point where the curve changes direction. It can be the highest point (in the case of a downward-opening parabola) or the lowest point (for an upward-opening parabola).

2. Other Terms:

   • Center: Generally refers to the center of a circle, not applicable here.
   • Directrix: A line used in the definition of a parabola but not a point.
   • Focus: A fixed point used in the definition of a parabola that helps in constructing the curve but is not the extreme point.

Thus, the correct answer is D. vertex.