Answer:
The correct answer is B
Step-by-step explanation:
Vitamin B12 requires intrinsic factor to be absorbed. This factor is secreted by parietal cells of the gastric mucosa. So it is common that patients who have had a gastrectomy develop this type of anemia.
Also Vitamin B12 is key to maturation of erythrocytes (red blood cells) and its deficiency leads to abnormal shapes (particularly more rounded erythrocytes). So options C and D can be rule out.