The most appropriate definition of a natural resource is that it is a substance/commodity that is

In a village in Karnataka,people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their fields in order to enhance the yield. Soon they discovered that the waterbody was completely covered with green floating plants and fishes started dying in large numbers. Analyse the situation and give reasons for the excessive growth of plants and the death of fish in the lake.

$(a)$ Why are coal and petroleum called fossil fuels?
$(b)$ Name any two elements present in fossil fuels in addition to carbon.

The main cause for abundant coliform bacteria in the river Ganga is

Select the incorrect statement.

Khadins,Bundhis,Ahars and Kattas are ancient structures that are examples for