Which phylum has members that secrete a hard, calcium carbonate shell?
- Arthropoda
- Nematoda
- Cnidaria
- Mollusca

i believe your answer would be Mollusca.

Explanation:

(i looked it up on britannica if you have any questions.) Mollusk, also spelled mollusc, any soft-bodied invertebrate of the phylum Mollusca, usually wholly or partly enclosed in a calcium carbonate shell secreted by a soft mantle covering the body.

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.

osteogenesis imperfecta (oi) refers to a congenital ailment of bones. in the condition, the bones become brittle or fragile. this ailment is a general result of the defect or mutations in the genes (colia1 or colia2). this mutation results in imperfect collagen formation either in quantity or quality wise.  

there are eight kinds of oi defects, and each kind varies with certain distinctions in symptoms. the usual symptoms include frequent bone fractures, loss of hearing in infants, protruding eyes, discoloration of the white in the eyes, respiratory issues, loosening of the joints, short stature, and other symptoms.