According to weins modification of the working length determination if bone resorption is there then:: (A) Reduce the length by 0.5mm, (B) Reduce the length by 1mm, (C) Reduce the length by 1.5mm., (D) Reduce the length by 2mm.
Answer is C. Wein modification of working length determination by radiograph: 
1. Reduce length by 1 mm if NO root + bone resorption 
2. Reduce length by 1.5 mm if bone resorption 
3. Reduce length by 2 mm if both root and bone resorption