Question

Microscopic organisms with calcium carbonate shells are called .

Answer 1

Foraminifera is a a single-celled planktonic animal with a perforated chalky shell through which slender protrusions of protoplasm extend. Most kinds are marine, and when they die, their shells form thick ocean-floor sediments.

Answer 2

nannoplankton would be the answer. (btw they are unicellular)