Which of these is the longest-lasting sink for carbon dioxide?

a. plant tissues and cellulose (the "woody" parts of plants)

b. the atmosphere

c. air bubbles within glacial ice

d. limestones?

Limestones are sedimentary rocks made of calcium carbonate which is in the form of calcite. It is formed in warm and shallow waters. It is an organic rock forming from shells as well as coral and debris. It also is form from chemical rocks that were formed by the precipitation of the mineral calcium carbonate from the water.