用活性炭管采集空气中的苯，以0.2L/min的流速采集10分钟（在标准状况下），用1ml二硫化碳解吸后，测得苯含量为20μg/ml，则空气中苯的浓度是（）

A.5mg/m₃

B.8mg/m₃

C.10mg/m₃

D.15mg/m₃

E.20mg/m₃

The newspaper says if more underground lines          next year, it will be much easier for people to travel around Nanjing.

A．will be finished

B．have finished

C．are finishing

D．are finished