Answer:
B. The locus of points equidistant from a given directrix and a focus
Step-by-step explanation:
A fixed point is a plane is a focus.A fixed line in a plane is a directrix.A set of all points in a plane that agree to a condition /property of lets say an equation is a locus.When these set of points in a plane are at equal distance to the directrix and a fixed point in the plane (that is not in the directrix) are joined the form a parabola.It takes a shape of a curve that can open up, down ,left or right.
See attached example
