If zzz satisfies ∣z−3∣=∣z−3i∣|z - 3| = |z - 3i|∣z−3∣=∣z−3i∣, what does this equation describe geometrically?
A circle centered at the origin.
A line y=xy = xy=x.
A line y=−xy = -xy=−x.
A circle centered at 3+3i3+3i3+3i.