VI. Insert the words from the list

transportation, vertical, construction, excavating, underground, tube, inside, portal, bottom, backfill

A tunnel is essentially horizontal … passageway produced by excavating or occasionally … by nature’s action in dissolving a soluble rock. A … opening is usually called a shaft. Tunnels have many uses: for mining ores, for … and for conducting water and sewage. True tunnels and chambers are excavated from the … and then lined as necessary to support the adjacent ground. A hillside tunnel entrance is called a …. Tunnels may also be started from the … of a vertical shaft or from the end of a horizontal tunnel driven principally for … access and called an adit. So-called cut-and-cover tunnels (more correctly called conduits) are built by … from the surface, constructing the structure, and then covering with …. Tunnels underwater are now commonly built by the use of an immersed ….

VII. Make the precis of the text.