Answer:
Light is at its greatest concentrations
Step-by-step explanation:
The coral reefs need several conditions so that they can survive. The most important though is the sunlight. The reason why the corals need sunlight is that they are performing photosynthesis, thus they need the sunlight to be able to do so. This sets a depth limit for the corals, as they can only survive at places where the sunlight can penetrate, thus in the shallow waters. It is also worth mentioning though that the majority of the corals also require warm waters to survive, but without the sufficient sunlight, the warm water will not help them a lot.