Which one of the following rightly defines mixing?

• A. Mixing converts a homogenous system to a heterogeneous system without adding any materials
• B. Mixing converts a heterogeneous system to a homogeneous system without adding any materials
• C. Mixing converts a heterogeneous system to a homogeneous system with or without adding any materials
• D. Mixing converts a heterogeneous system to a homogeneous system with or without adding any materials