—Isn’t it a great surprise that I happened to meet my university English teacher at the South Bank Parkland last week?

—How long ____ you _____ each other, then?

A．hadn’t; seen

B．haven’t; seen

C．didn’t; see

D．don’t; see

货流在时间分布上的不平衡性可以用______指标衡量。

A．回运系数
B．货流量密度
C．运量不平衡系数
D．行程利用系数