Newborns can be protected against certain digestive and respiratory infections when they receive what via their mother's milk? This antibody is also present in secretions like tears and nasal fluid.

A. Diapedesis (transmigration): the cell is shown squeezing through the vessel wall (leaving the bloodstream), which is diapedesis (also called extravasation).
B. Phagocytosis: phagocytosis is ingestion of particles/pathogens by a phagocyte; the image shows movement out of a vessel, not engulfment of material.
C. Chemotaxis: Incorrect (related but not the pictured action) -chemotaxis is directed movement toward chemical signals; a leukocyte may chemotax once in the tissue, but the image specifically shows the mechanical passage through the endothelium (diapedesis).
D. Margination/Rolling: margination/rolling are earlier steps along the endothelium where leukocytes slow and adhere; the image shows a cell already squeezing through the wall, which is the next step (diapedesis).

A. Megakaryocytes: Megakaryocytes are large bone marrow cells whose cytoplasmic fragments become platelets (thrombocytes).
B. Macrophages: Phagocytic cells derived from monocytes; they do not produce platelets.
C. Monoblasts: Immature precursors that develop into monocytes/macrophages, not platelets.
D. Reticulocytes: Immature red blood cells (RBC precursors) released from bone marrow—not a source of platelets.