Concept:
Ligands may be neutral, anionic, or cationic depending on their charge.
Step 1: Check each ligand.
• Nitrato = \(\text{NO}_3^-\), so it is anionic.
• Cyano = \(\text{CN}^-\), so it is anionic.
• Aqua = \(\text{H}_2\text{O}\), so it is neutral.
• Iodo = \(\text{I}^-\), so it is anionic.
Step 2: Identify the neutral ligand.
The neutral ligand is:
\[
\text{H}_2\text{O}
\]
which is called aqua.
Hence, the correct answer is:
\[
\boxed{(C)\ \text{Aqua}}
\]