I want to know the answer to the following question:
What is the main example of a DC power source?
All the background I'm provided with is that "Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators.". Is that enough to answer the question?