The old professor told us that every part of the materials should be made use of _____ the station. [ ]

A. building

B. to build

C. build

D. being built

一污水排放量为30000m³/d的建设项目向某大型河流排放污水，则对该河流进行环境现状调查的范围应为( )。

A．20～40km

B．15～30km

C．10～20km

D．5～10km