Which detail from the passage strengthens the author's idea that coquina stone was a historically significant finding?

A.
Since no one has ever built a fort or any large building out of coquina, they have no idea how strong it would be. (paragraph 6)
B.
Instead of shattering, the coquina stone merely compresses and absorbs the shock of the hit. The cannon balls just bounce off or sink in a few inches. (paragraph 7)
C.
Thousands of years ago, the tiny coquina clam (donax variabilis) lived in the shallow waters of coastal Florida, as they still do today. These are the small pink, lavender, yellow, or white shells one sees along the beach at the waterline. (paragraph 2)
D.
This material "glued" the shell fragments together into a porous type of limestone we now call coquina, which is Spanish for "tiny shell". (paragraph 3)