铁路轨道是线路的上部建筑，包括钢轨、轨枕、联结零件、道床、防爬设备。
参考答案：错
五脏六腑之大主指的是（）。
A.肾
B.肝
C.心
D.脾
E.肺
The twin towers fell down. It looked_____ a huge piece of chocolate had been melted down(溶化).
A．as though
B．even though
C．in case
D．if
