I started as ________ office clerk, and turned ________ department manager three years later.

A．the; the

B．an; a

C．an; /

D．the; /

下列估测值最接近实际的是 [ ]

A．九年级物理课本长约6cm

B．一名中学生体重约为500N

C．人步行速度约5m/s

D．你所处考场现在的气温约为10℃