Which of the following is a static source of water for firefighting?

The correct choice identifies that all the provided options represent static sources of water suitable for firefighting. Static water sources are those that do not have flowing currents, meaning they are relatively still bodies of water that can be utilized when battling fires.

Lakes are large bodies of freshwater surrounded by land, providing a significant amount of water that can be drawn for firefighting without concern for flow dynamics. Oceans, while saline, offer vast amounts of water that can also be harnessed, though considerations for equipment and environmental impacts must be taken into account due to the saltwater's corrosive nature. Swimming pools, while smaller, also serve as effective static water sources, typically being sheltered and easily accessible.

Hence, when assessed collectively, lakes, oceans, and swimming pools all qualify as static sources of water, making the selection of all options valid and reinforcing the understanding that any of these bodies can be employed in firefighting operations.