Answer- A. MRIEwingts sarcoma:MRI is essential to elucidate soft-tissue involvement in Ewing's sarcoma, because the tumor has low signal intensity on Tl-weighted images compared with the normal high signal intensity of the bone marow.Osteomyelitis:MRI allows early detection of osteomyelitis and assessment of the extent of involvement and the activity of the disease in cases of chronic bone infection.It is considered the most useful imaging technique to evaluate suspected osteomyelitis because of its ability to demonstratechanges in the water content ofbone marrow with an excellent structural definition and spatial resolution.