If the following events were placed in chronological order which would come fourth?

The answer is C. A minor skin infection often caused by penicillin resistant Staphylococcus aureus (B) results in blood spread to the bone marrow (E) from where infection spreads through the cortical bone to produce a subperiosteal abscess (D); the presence of pus may result in thrombosis of the nutrient artery which causes death of the diaphyseal bone which forms the sequestrum (C). New bone is produced under the periosteum, forming an encasing sheath of irregular outline, the involucrum (A).