Answer: B
Explanation:
A parabola is defined using both a directrix and a focus.
To justify this, let me take a quote from Varsity Tutors (all credit of this quote goes to them) : “A parabola is set of all points in a plane which are an equal distance away from a given point and given line. The point is called the focus of the parabola and the line is called the directrix.”
Hope this helps! :)