The marrow shows precursors to erythrocytes, as well as megakaryocytes. This is to show you that the issue isn't underproduction, which means that we are losing RBC and platelets somewhere ie destruction. That rules out D and E. There is nothing to indicate tha the child has disseminated tuberculosis (B). At this point we are left with A or C. A would indicate Disseminated Intravascular Coagulation (DIC) or something similar, which would result in low platelets and RBC but we would also see abnormal RBC like schistocytes ("helmet" cells). We are explicitly told that the erythrocytes are normochromic and normocytic. However, immune destruction of platelets explains it all- the destruction of platelets leads to some hemorrhaging and so a drop in RBC, and ITP classically arises after a recent upper respiratory tract viral infection.

Why is this not HUS? How did you guys approach the question?

What are we supposed to be looking at? I see multinucleated giant cells. I also see infiltrate (can’t tell if this is mononuclear or not).