The systemic circuit:

Macrophages are the main cells that clear out the cell debris by phagocytosis, a process that involves recognition, engulfment, and degradation of the disposable particles.

Macrophages are professional phagocytes that can be found in various tissues and organs, where they perform efferocytosis, the removal of dead and dying cells.

Choice A is wrong because lymphocytes are not phagocytes, but rather immune cells that mediate adaptive immunity by producing antibodies or killing infected cells.

Choice B is wrong because cytokines are not cells, but rather soluble molecules that regulate inflammation and immunity by acting as signals between cells.

Choice C is wrong because mast cells are not primarily involved in clearing cell debris, but rather in allergic reactions and innate immunity by releasing histamine and other mediators.

This is because anatomy and physiology are closely related branches of biology that study the structure and function of living organisms respectively.
Anatomy describes the shape, size, location, and relationships of body parts, while physiology explains how those parts work together to maintain life.
For example, the anatomy of the heart determines how it pumps blood, and the anatomy of the lungs determines how they exchange gases.
Choice B is wrong because our understanding of both anatomy and physiology is constantly changing as new discoveries are made in the field of biology.
Choice C is wrong because body parts take up space regardless of their physiological functions.
Choice D is wrong because physiological functions are not limited to an organism, but can also occur at the cellular, tissue, organ, and system levels.