放射性种籽植入治疗常用永久性植入的放射性核素为（）。
A.226Ra
B.193Ir
C.60Co
D.125I
E.137Cs
参考答案：D
— Johnson, come and look at the sea! It is beautiful, isn't it?
— Absolutely! If only I _____ here by the sea. [ ]
A. lived
B. live
C. had lived
D. will live
轨枕间距是根据什么确定的？
