Step 1: Recall the types.
Multi-molecular colloids form when many small atoms cluster together. Macromolecular colloids are big single polymer molecules. Associated colloids are micelles formed at higher concentration.
Step 2: Sort the options.
Nylon and cellulose are large polymers, so macromolecular. Soap forms micelles, so associated. Gold sol is many gold atoms grouped together.
Step 3: Pick.
Gold sol is the multi-molecular colloid.
\[ \boxed{\text{Gold sol, option 2}} \]