A
Islands of bone within the soft tissues about the hip
B
Bone spurs from the pelvis or femur leaving more than 1 cm between opposing bone surfaces
C
Bone spurs leaving less than 1 cm between opposing bone surfaces
D
Apparent radiographic bony ankylosis of the hip joint
Explanation:Correct Option: D. The Brooker classification grades HO from I to IV based on AP pelvic radiographs. Grade I: islands of bone in soft tissue. Grade II: bone spurs leaving >1cm between opposing surfaces. Grade III: bone spurs leaving <1cm between opposing surfaces. Grade IV: complete apparent radiographic bony ankylosis of the joint. (Ref: Brooker et al., J Bone Joint Surg Am, 1973)