Select the eco-friendly activity among the following.

Which of the following is an endangered bird species?

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

The $pH$ of a water sample collected from a river was found to be acidic in the range of $3.5-4.5$. On the banks of the river were several factories that were discharging effluents into the river. The effluents of which one of the following factories is the most likely cause for lowering the $pH$ of river water?

Which plant leaves are used to make $Bidis$?

Name any two wastes which can be recycled and reused.