—How far is it from the railway station to the hotel?

—It's about _______ walk. [ ]

A. ten minute's

B. ten-minutes

C. ten minutes'

D. ten minutes

标准正态分布曲线的特征是

A．μ＝0，σ=l

B．μ=1，σ=0

C．μ＝0，σ=0

D．μ＝1，σ＝1

E．μ＝0，σ值不确定