A:to buy
B:which to buy
C:for him to buy
D:with which to buy
地球上最大的生态系统是( )
已知随机变量ξ的概率分布如下,则P(ξ=10)=( )
ξ
1
2
3
4
5
6
7
8
9
10
P
23
232
233
234
235
236
237
238
239
m