Would You Use a Physical Model or a Conceptual Model

Would you use a physical model or a conceptual model to describe the following: a gold coin, dollar bill, car engine, air pollution, virus, spread of sexually transmitted disease?

A) conceptual model-gold coin, car engine, virus; physical model-air pollution, spread of sexually transmitted disease, dollar bill
B) physical model-gold coin, car engine, virus; conceptual model-air pollution, spread of sexually transmitted disease; dollar bill, which could represent wealth, may well be described by either model.
C) physical model-gold coin, dollar bill, car engine; conceptual model-virus, air pollution, spread of sexually transmitted disease
D) You could adequately describe all of the topics by either model. The choice depends only on the characteristics requiring description.