Which navigation light shines forward and is required on all power-driven vessels?

The masthead light is the correct choice as it is specifically designed to shine forward on power-driven vessels. This light is an essential part of a vessel's lighting arrangement and helps to indicate the presence of the vessel to other boats and to identify its direction of travel. It is typically positioned at the highest point of the vessel, providing visibility from a distance.

Vessels are required to have a masthead light to comply with maritime navigation rules, ensuring safe navigation, especially during nighttime or reduced visibility conditions. This light's primary purpose is to signal to others the forward direction of the vessel, which is critical for preventing collisions.

Other lighting options serve different functions. The sternlight is mounted at the rear of the vessel and is not visible from the front. An all-round white light emits light in all directions but does not specifically indicate forward motion. Sidelights, which indicate the port and starboard sides of the vessel, also do not shine directly forward. Thus, the masthead light is the only light required on power-driven vessels that serves this forward-facing purpose.