单项选择题
A.6000R B.6500R C.7000R D.7500R E.8000R
A.2cm;2cm B.1cm;2cm C.2cm;1cm D.1cm;1cm E.2cm;1.5cm
A.4~15MeV B.10~25MeV C.10~20MeV D.4~25MeV E.4~20MeV