It is believed that            part of animals can’t stay alive in water at 1,500 meters below ____

sea level.

A．不填；不填

B．a; a

C．the; the

D．不填; the

路基（）等地表排水设施应与天然沟渠和相邻的桥涵、隧道、车站等排水设备衔接配合，组成完整的排水系统。