Which of the Following Is True of How Is Anemia

Which of the following is true of how is anemia caused?

A) Anemia may be caused by a deficiency in the amount of hemoglobin that occurs when the number of circulating red blood cells decreases.
B) Anemia may be caused by excessive blood loss or by an increase in the destruction of red blood cells (RBCs) .
C) Anemia may be caused by a decrease in the production of RBCs, which reduces the amount of circulating hemoglobin.
D) All of these statements are correct.