Answer:
x^2 + y^2 = 20
Explanation:
It should be obvious that the center of this circle is located at the origin: (0, 0).
Thus, the general form of this circle is x^2 + y^2 = r^2, where r is the radius.
Note that the radius is more than 4 but less than 5.
Thus, r^2 must be more than 4^2 and less than 5^2, or
more than 16 and less than 25.
Answer A fits this description: x^2 + y^2 = 20.