设随机变量X的分布律为则概率______.
A、0.2
B、0.4
C、0.6
D、0.8

单项选择题The 21st vertebra refers to the ( ) in TCM literature. A、The 2nd lumbar vertebra B、The 4th lumbar vertebra C、The 12th thoracic vertebra D、The 2nd sacral vertebra E、The 4th sacral vertebra

单项选择题A． B．2 C．0 D．1