The answer should be altitude
The answer is; fossil
Fossil is defined as any dead organism ( or its trace or impression) of a past geological time that is naturally preserved in the earth in geological features such as rocks, bogs, and etcetera. Coral reef is no exception because it is considered a living organism. It is composed of colonies of coral polyps and algae that secrete a carbon carbonate skeleton.
<span> water is a solvent. It helps to break waste and nutrients down in the </span>cell so <span>that they can be moved through the various membranes. this is necessary in a cell </span><span />
The youngest would be the ones at the top and the oldest would be at the bottom. the oldest is B and the ones around it, as they get bigger get younger. hope this helps :)