In the attached diagram you can see all four possible placement of a parabola with vertex at origin.
You know that parabola has a focus on the negative part of the y-axis. Then you chould consider the 4th placement of parabola.
As you can see the directrix crosses through the positive part of the y-axis. (Option A is true).
The equation of parabola is [tex] y=-4ax^2 [/tex], where a is a positive number, then all four remaining options are false, because each of these options gives you wrong equation of parabola.
Answer: correct choice is A.
