Which natural resource is depleting rapidly in the world?

What measures would you take to conserve electricity in your house?

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?

List any four methods of conserving fossil fuels.

What do the three $R$s refer to in order to save the environment? Which one of these would be the best for the environment?

"Sustainable development depends upon the willingness of the people to change their perception of the socio-economic and environmental conditions around them:" Justify the statement.