The method to diagnosis misplaced intra uterine device is
D i.e. All of above Investigation of choice in displaced IUD is Ultrasound, but we can also diagnose this by X-Ray abdomen (metal in IUD produces radioopaque shadow) & Hysteroscopy (Endoscopic visualization of uterus).
Ultrasound
X-Ray abdomen (Erect view)
Uterine sound & Hysteroscopy
All of the above