根据《行李包裹事故处理规则》，行李、包裹查询电报、复电、答复书保管（）。
A.6个月
B.12个月
C.18个月
D.24个月
参考答案：D
With all my attention _____ my homework, I didn't even notice my father standing by me.
A．to fix on
B．fixed on
C．fixing on
D．to be fixed on
简述如何处治通道混凝土出现的裂缝、渗水的问题？
