69.就穿透深度來說，下列各種治療機由高至低的排列順序，何者正確？ (A)supervoltage＞megavoltage＞orthovoltage＞superficial (B)megavoltage＞supervoltage＞superficial＞orthovoltage (C)megavoltage＞supervoltage＞orthovoltage＞superficial (D)orthovoltage＞supervoltage＞superficial＞megavoltage 131