Where was the World Summit on Sustainable Development held in $2002$?

The salinity of the oceans is

Consider the following statements about Ramesh Chandra Dagar's work in the field of organic farming:
$I.$ Ramesh Chandra Dagar's work includes bee-keeping,dairy management,water harvesting,composting,and agriculture in a chain of processes.
$II.$ In this process,there is no need to use chemical fertilisers for crops as cattle excreta is used as manure.
$III.$ Crop waste is used for making compost,which is used as natural fertilizer.
$IV.$ Compost generates natural gas,which is used for the energy needs of the farm.
Which of the statements given above are correct?

$A$ - $BOD$ is a measure of the organic matter present in the water.
$R$ - The lower the $BOD$ of water,the lower is its polluting potential.

$LPG$ stands for Liquefied Petroleum Gas,which is primarily composed of propane and butane. What is the nature of $LPG$?

Match the following and choose the correct combination from the options given:
Column $I$ | Column $II$
$(1)$ $DDT$ | $(p)$ $CO, CO_2$
$(2)$ $PAN$ | $(q)$ Smog
$(3)$ Acid rain | $(r)$ Biological magnification
$(4)$ Global warming | $(s)$ $SO_2$