Yesterday morning ,Jim hurried to the station .He was very angry __ the  train had just left.[ ]

A. and  

B. so

C. because

D. so that

两样本比较的秩和检验中，备择假设为（）

A.两个样本的总体均数不同

B.两个样本的总体分布相同

C.两个样本的总体分布不同

D.两个样本的总体均数相同

E.差值总体中位数不为0