D is the answer to this question. You should first understand what this is. This is known to be the last stage of the red blood cell precursor. When people show that they have this type of red blood cells in their system, this usually signifies that they have a disease with a possible poor prognosis.
It is a bit of a surprise that this type of cell can sometimes be seen in some dog breeds but do remember that it is not available in high amounts. There are different reasons why this may appear in humans. It may be because of a tumor or it can also be because the person is suffering from severe anemia.