Correct Answer:
B. Chalk
The correct answer is Chalk. Foraminifera are single-celled marine protists that produce intricate shells, known as tests, primarily composed of calcium carbonate. When these organisms die, their calcium carbonate shells accumulate on the seafloor over vast periods, eventually compacting and cementing to form chalk, a type of soft, porous limestone.
- Silica shells are typically produced by other marine microorganisms like diatoms and radiolarians, not foraminifera.
- Cellulose walls are characteristic of plant cells, providing structural support, and are not produced by foraminifera.
- Protein structures are fundamental to all living organisms, but foraminifera's primary external structural output is calcium carbonate shells, not generalized protein structures.