(来学网)国际电工委员会规定,真实声束声强lob关于胎儿是
  • A.
    (来学网)lob小于100mW/cm2
  • B.
    (来学网)lob小于20mW/cm2
  • C.
    (来学网)lob大于50mW/cm2
  • D.
    (来学网)lob大于30mW/cm2
  • E.
    (来学网)lob大于150mW/cm2