The smooth, thin membrane that lines the chambers of the heart and forms the surface of the heart valves is the:

A monocyte is a type of white blood cell that is markedly larger than a red blood cell and has a large kidney-shaped nucleus.

Monocytes are involved in defending the body against infectious diseases and foreign materials.
Choice B is wrong because a basophil is a type of granular white blood cell that has a lobed nucleus and stains purple with basic dyes.
Basophils are involved in allergic reactions and inflammation.
Choice C is wrong because a neutrophil is a type of granular white blood cell that has a multilobed nucleus and stains pale pink with neutral dyes.
Neutrophils are involved in phagocytosis and killing bacteria.
Choice D is wrong because an eosinophil is a type of granular white blood cell that has a bilobed nucleus and stains red-orange with acidic dyes.
Eosinophils are involved in combating parasitic infections and allergic responses. The normal ranges of different types of blood cells are:
Red blood cells: 4.5 to 5.9 million per microliter (mcL) for males, 4.1 to 5.1 million per mcL for females
White blood cells: 4,000 to 11,000 per mcL for both males and females
Platelets: 150,000 to 450,000 per mcL for both males and females

This is because erythroblastosis fetalis, also known as hemolytic disease of the newborn, is caused by Rh incompatibility between the mother and the fetus.
Rh incompatibility occurs when a Rh-negative mother is impregnated by a Rh-positive father, resulting in a Rh-positive fetus.
The mother’s immune system can detect the Rh factor on the fetus’s red blood cells as foreign and produce antibodies against them.
These antibodies can cross the placenta and destroy the fetus’s red blood cells, causing anemia, jaundice, edema, and other complications.
Choice A is wrong because a second Rh-negative fetus developing in an Rh-negative woman will not cause erythroblastosis fetalis.
The mother and the fetus have the same Rh factor, so there is no immune reaction.
Choice C is wrong because a first Rh-positive fetus developing in an Rh-negative woman will not cause erythroblastosis fetalis.
The mother’s immune system will not produce antibodies against the Rh factor until after the first exposure to it, which usually happens during delivery.
Therefore, the first pregnancy is usually unaffected.
Choice D is wrong because a first Rh-negative fetus developing in an Rh-negative woman will not cause erythroblastosis fetalis.
The mother and the fetus have the same Rh factor, so there is no immune reaction.

The normal range of red blood cell count for newborns is 4.1 to 6.1 million cells per microliter of blood.
The normal range of bilirubin level for newborns is 0.3 to 1.9 milligrams per deciliter of blood.