骨巨细胞瘤治疗方案的确定，决定于（）
A.X线表现
B.临床表现
C.G、T、M分级
D.病理检查
E.放疗后有否恶变
参考答案：C
为防止牵引供电设备对信号设备的干扰，采取了哪些防护措施？
I'm afraid Mr. Harding _____ see you now. He's busy. [ ]
A. can't
B. mustn't
C. shouldn't
D. needn't
