Which maintains an area’s water supply?

The bridge that is used to span wide rivers are:

The whole length and breadth of the country is connected with a net work of:

When heavy snow slides down a mountain, it is called:

An open place or a  covered building where buyers  and  sellers convene for the  sale of goods is called a:

When the soil is  blown away by the wind or washed away by the rain, it is called:

Which is a natural change?

Soil erosion can be reduced by:

Water collects in cracks and freezes and causes the rocks to break  to form:

Which bridge is a supported structure?