question: A 15-year-old girl complains of headaches since 2 months. Earlier occurred 1—2 times a week but now up to five episodes  a week experienced, not associated with any neurological , visual disturbances, nausea or vomiting. The girl also reports a white discharge from both of her nipples. She has not started menstruating. The most appropriate investigation is:
opa: Lateral skull x-ray
opb: CT scan
opc: MRI scan
opd: Serum prolactin measurement