Answer: A diameter (a line parallel to axis).
- A Another parabola congruent to the original one
- B A diameter (a line parallel to axis)
- C A circle centred at the parabola's focus
- D The axis of the parabola itself, exactly
Correct answer: B. A diameter (a line parallel to axis)
Explanation: The locus of midpoints of parallel chords of a parabola is a line parallel to the axis of the parabola (a diameter of the parabola).
The slope of a line is the ratio of vertical change (rise) to horizontal change (run) between any two points on it - equivalently, the tangent of the angle θ the line makes with the positive x-axis.