Much of the world's limestone comes from the in the skeletons of

Much of the world's limestone comes from the fresh water in the skeletons of the marine organisms. it is usually the accumulation of the debris of coral , shell and other marine animals. it can also be formed in cave when water evaporated that has high content of calcium carbonate

I can help if you tell me what its about.

it supports cell theory.it states that all living cells are made from cells