Oral communication is communicating by speech.
Answer:
A. There are no excess materials stored in warehouses
Explanation:
It will be difficult to publicize and market "print on demand (POD)" materials because there are no warehouses were buyers can visit to purchase the excess materials stored at their convenience.
Actually, print on demand eliminate warehouses. This is because materials are printed whenever people order. So, it's likely things are done digitally. Even publication fees are paid online. So, with such in place, publicizing the material or marketing it becomes difficult.
