A newborn is protected against certain digestive and respiratory infections by IgA received via the mother:

Basophils usually account for the smallest percentage of leukocytes in a blood sample. Basophils are a type of white blood cell that is involved in allergic reactions and inflammation.
Choice A is wrong because eosinophils are not the least common type of leukocyte.
Eosinophils are another type of white blood cell that is involved in allergic responses and parasitic infections.
They typically make up about 1-6% of the total leukocyte count.
Choice B is wrong because monocytes are not the least common type of leukocyte.
Monocytes are a type of white blood cell that can differentiate into macrophages and dendritic cells, which are important for phagocytosis and antigen presentation.
They typically make up about 2-10% of the total leukocyte count.
Choice D is wrong because neutrophils are not the least common type of leukocyte.
Neutrophils are a type of white blood cell that are the first responders to bacterial infections and tissue damage.
They typically make up about 55-70% of the total leukocyte count.

A newborn is protected against certain digestive and respiratory infections by IgA received via the mother’s milk.
IgA is the main antibody found in breast milk, and it coats and seals the baby’s respiratory and intestinal tract to prevent germs from entering the body and bloodstream.
Choice A is wrong because the blood does not contain IgA, which is the main antibody that protects mucosal membranes.
Choice B is wrong because the placenta does not transfer IgA to the fetus, but only some other antibodies such as IgG.
Choice D is wrong because the intestine does not produce IgA in newborns, as they are born with low levels of IgA.