By definition, the Standard form of the equation of an ellipse is:

Where the center is:

When its center is at the Origin, the equation is:

When:

Where:

It is horizontal.
And when:

Where:

It is vertical.
In this case, you know that this ellipse is centered at the Origin, its vertex is:

And the co-vertex is at:

Analyzing the information given in the exercise, you can idenfity that:

Therefore, you can substitute values into the equation

You get:

The answer is: Last option.