Step-by-step explanation:
The density of the material is given by,
Density = 

Case 1: Rock
Density = 

Density = 

Density = 2000 

Case 2: Pillow
Density = 

Density = 

Density = 20 

Case 3: Bottle of Soda
Density = 

Density = 

Density = 1000 

Case 4: Load of bread
Density = 

Density = 

Density = 100 

Thus, rock and bottle of soda has maximum density.