单项选择题
60钴治疗机灯光野边界与照射边界之间偏差不超过()
A.1mm B.1.5mm C.2mm D.2.5mm E.3mm
A.1mm B.2mm C.3mm D.0.5mm E.1.5mm
A.5mm B.10mm C.15mm D.20mm E.25mm