Which of the following is an example of direct current (DC)?

Direct current (DC) is characterized by the flow of electric charge in a single direction, which is a fundamental attribute of both batteries and certain types of power supplies. In the case of batteries, they convert chemical energy into electrical energy, providing a steady and unidirectional flow of electrons. This consistent flow makes batteries a prime example of direct current.

Alternatively, electricity produced by generators typically refers to alternating current (AC), which oscillates back and forth. Electricity supplied by the grid is also alternating current, as this is the standard form for distribution because it is more efficient for transmission over long distances. Static electricity, while it may involve a charge, does not represent a current flow in the continuous manner that defines direct current.

Therefore, batteries are the most straightforward example of direct current since they deliver a constant voltage and current in one direction.