In what situation would a power-driven vessel display sidelights and one tow light?

Answer: C — While pushing ahead or towing alongside

A power-driven vessel is required to display sidelights and a tow light when it is engaged in towing operations, particularly when it is pushing ahead or towing alongside another vessel. The sidelights indicate the presence of the vessel and its direction, with the green light indicating the starboard side and the red light indicating the port side. The tow light, typically white and displayed above the sidelights, signifies that the vessel is engaged in towing. This combination of lights not only helps in identifying the vessel's capabilities but also provides essential information to other vessels regarding its function and navigation. In situations like sailing in open waters, being at anchor, or maneuvering through a narrow channel, different lighting configurations are required. For instance, at anchor, a vessel would display a single white light and not the sidelights or tow light. Similarly, the requirements for maneuvering through narrow channels would differ based on the specific circumstances and the types of vessels involved.