ANS:A - soft ground

1) Running ground: Requires instant support throughout the excavation. Examples include dry sand, gravel, silt, mud, and water-bearing sand.

2) Soft ground: Requires instant support for the roof but the walls can do without support for a few minutes. Examples include damp sand, soft earth, and certain types of gravel.

3) Firm ground: The sidewalls and face of the tunnel can do without support for one or two hours, but the roof can last only a few minutes. Examples include firm clay, gravel, and dry earth.