专用优质碳素结构的牌号中，( )表示桥梁用钢。
A．HP
B．g
C．H
D．q
参考答案：D
, I lost heart in English learning, but my teacher often said to me, “Keep on studying hard , and you’ll succeed .”
A．At one time; in time
B．At one time; on time
C．At a time; in time
D．At a time; on time
ACARS数据链系统的工作频率是（）
A、128.6MHz
B、121.5MHz
C、130MHz
D、131.45MHz
