What is the domain of the relation graphed below?

On a coordinate plane, an ellipse intercepts the x-axis at (negative 4, 0) and (4, 0) and intercepts the y-axis at (0, 1) and (0, negative 1).
domain: StartSet x vertical line x belongs to all natural numbers EndSet
domain: StartSet x vertical line x belongs to all real numbers EndSet
domain: StartSet x vertical line negative 4 less-than-or-equal-to x less-than-or-equal-to 4 EndSet
domain: StartSet x vertical line negative 1 less-than-or-equal-to x less-than-or-equal-to 1 EndSet