Final answer:
The sunlit zone changes to the twilight zone at a depth of approximately 200 meters in the ocean.
Step-by-step explanation:
The sunlit zone changes to the twilight zone in the ocean at a depth of approximately 200 meters. This depth marks the end of the photic zone, where light can penetrate, and the beginning of the aphotic zone, where light cannot penetrate. In the aphotic zone, there is not enough sunlight for photosynthesis to occur, so organisms rely on other sources of energy, such as chemosynthesis or organic matter falling from the surface.