It is reported that the railway _____ now will cut the journey time between the two cities by about 12 hours.

A．built

B．to be built

C．having built

D．being built

假设人体的头部可看作球形，若某人头部三分之一的面积覆盖头发，头发密集程度为25根/厘米²则该人头发数量约为______根（球的面积公式S=4πr²）．

在一玻璃缸中装着煤油和水两层液体，一块浮冰悬浮在油水分界面之间，浮冰熔化后，煤油液面将______，油水分界面将______．