Looser zones (pseudofractures) observed on plain radiographs of the femoral neck or pubic rami are pathognomonic for which of the following metabolic bone disorders?

Explanation:
The correct option is a. Looser zones, also known as pseudofractures or Milkman lines, are wide, transverse radiolucent bands that traverse part of the bone, frequently seen on the compression side of the femoral neck, pubic rami, or ribs. They are a classic radiographic hallmark of osteomalacia and represent accumulations of unmineralized osteoid along penetrating blood vessels. Reference: Mankin HJ. Metabolic bone disease. J Bone Joint Surg Am.