单选题
设随机变量
且满足P(X
1
X
2
=0)=1，则P(X
1
=X
2
)等于______．
A．0
B．
C．
且满足P(X
1
X
2
=0)=1，则P(X
1
=X
2
)等于______．
A．0
B．
C．
【正确答案】
A
【答案解析】[解析] 由题意得
P(X 1 =-1，X 2 =-1)=P(X 1 =-1，X 2 =1)=P(X 1 =1，X 2 =-1)=P(X 1 =1，X 2 =1)=0
P(X 1 =-1，X 2 =0)=P(X 1 =-1)=
，P(X
1
=1，X
2
=0)=P(X
1
=1)=
，
P(X 1 =0，x 2 =-1)=P(X 2 =-1)=
，P(X
1
=0，X
2
=1)=P(X
2
=1)=
P(X 1 =-1，X 2 =-1)=P(X 1 =-1，X 2 =1)=P(X 1 =1，X 2 =-1)=P(X 1 =1，X 2 =1)=0
P(X 1 =-1，X 2 =0)=P(X 1 =-1)=
，P(X
1
=1，X
2
=0)=P(X
1
=1)=
，
P(X 1 =0，x 2 =-1)=P(X 2 =-1)=
，P(X
1
=0，X
2
=1)=P(X
2
=1)=