What is the definition of a Path

A．A sequence of vertices and the edges formed by each successive pair of vertice

B．A walk with distinct vertice

C．A walk with distinct edge

D．None of the above

决定放射性核素有效半衰期的因素是（）

A.粒子的射程

B.物理半衰期和生物半衰期

C.淋洗时间间隔

D.断层重建方式

E.测量系统的分辨时间