Step 1: Understanding the Concept
Intensive properties are independent of the quantity of substance, for example density, temperature and pressure.
Step 2: Check the options
Mass, internal energy and number of moles all increase with the amount of substance, so they are extensive.\nDensity is mass per unit volume and stays the same for any amount.
Final Answer:
Density is an intensive property.
\[ \boxed{\text{(A) }\text{Density}} \]