Coral formations .

A. tend to occur poleward of 30° latitude
B. survive in a broad ecological range because they are tolerant of temperature, salinity, and depth variation
C. require water that is high in sediment concentration
D. are made of animals living symbiotically with simple algae

D. are made of animals living symbiotically with simple algae

Explanation:

Coral formations are made of animals living symbiotically with simple algae

The formation of Corals commenced when free-swimming coral larvae merges to submerged rock or other available surfaces along the edge of a island or continents.

Coral formation are generally divided in four classes by the scientist, They are:

1)Fringing reefs

2) Barrier reefs

3)atolls reefs

4)patch reefs