the students in this primary school is about four thousand, and           of them are boys.[ ]

A. A number of; three fifth

B. A number of; three fifths

C. The number of; three fifth

D. The number of; three fifths

两组独立样本资料的t检验，差别有统计学意义时，P值越小，说明（）

A.两样本均数差别越大

B.两总体均数差别越大

C.两总体均数是相同的

D.越有理由认为两样本均数不同

E.越有理由认为两总体均数不同