Multiple Choice: The graph of $x^2 + y^2 = 4$ is:  

1. A parabola with $y$-intercept $\left(0,4\right)$.

2. A circle with radius $4$ and center $\left(0,0\right)$.

3. A parabola with $x$-intercepts $\left(-2,0\right)$ and $\left(2,0\right)$.

4. A circle with radius $2$ and center $\left(0,0\right)$.

5. none of these