55.就穿透深度來說，下列各種治療機的排列順序（由高至低），何者正確？
(A)supervoltage＞megavoltage＞orthovoltage＞superficial
(B)megavoltage＞supervoltage＞superficial＞orthovoltage
(C) megavoltage＞supervoltage＞orthovoltage＞superficial
(D)orthovoltage＞supervoltage＞superficial＞megavoltage