干线子系统也可称为( )。
A．垂直子系统
B．水平子系统
C．平行子系统
D．交错子系统
参考答案：A
Zliaozhou Bridge _______ has been there for over 1300 years still looks nice. [ ]
A. which
B. what
C. whose
D. who
倒闸操作票由监护人填写。第十一章
