Final answer:
The domain D4 is a multiply connected region in the complex plane, defined as the set of complex numbers z satisfying specific conditions.
Step-by-step explanation:
The domain D4 can be defined as the set of complex numbers z in the complex plane such that the distance from z to the origin is less than 4, excluding the region between the circles centered at i and -i with radii of 1/2.
To sketch and classify the domain, we can visualize the complex plane and shade the region that satisfies the given conditions. The region inside the circle centered at the origin with radius 4 should be shaded, except for the region between the two smaller circles. This shaded region represents the domain D4.
Based on the definition and visualization, the domain D4 is classified as multiply connected since it contains a region with a hole.