肢体各层面放大率不同，计算放大率的依据是

A．远端面皮肤面至胶片或IP板、平板探测器的距离
B．近端面皮肤面至胶片或IP板、平板探测器的距离
C．肢体厚度1/2处至胶片或IP板、平板探测器的距离
D．体表可触标志点至胶片或IP板、平板探测器的距离
E．欲放大病灶中心至胶片或IP板、平板探测器的距离

History is ( ) a subject that only lets us know something in history; it also tells us a lot of truth.

A．less than

B．more than

C．no more than

D．not more than