Final answer:
The zero-sequence network impedance for a balanced Y-load is very low (C).
Step-by-step explanation:
The zero-sequence network impedance for a balanced Y-load is very low (C). In a balanced Y-load, the zero-sequence current flows in the neutral wire, which means that the impedance seen by this current is determined by the impedance of the neutral wire. The neutral wire is typically designed to have very low impedance in order to facilitate the flow of zero-sequence current.