不属于物流公共信息平台特征的是()
A. 层次性
B. 开放性
C. 区域性
D. 动态性
It was two years ago _____ his sister became a doctor.
A. that
B. where
C. who
D. when
第一磨牙完全萌出后最好在什么时候进行窝沟封闭
A. 6-7岁
B. 8-9岁
C. 9-10
D. 10-11
令信道输入端熵为H(X),输出端熵为H(Y),若该信道为无噪有损信道,其信道容量为
A. H(X)
B. H(Y)
C. H(XY)
D. I(X;Y)