Which one of the following pairs is wrongly matched?

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Silage	$(P)$ Measure of water pollution level
$(2)$ Flocs	$(Q)$ Cattle feed
$(3)$ Biogas	$(R)$ Bacteria associated with fungal filaments
$(4)$ $BOD$	$(S)$ Anaerobic metabolism of organic waste

Match the columns:

Column-$I$	Column-$II$
$(a)$ Mycorrhiza	$(1)$ Rhizobium
$(b)$ Bt	$(2)$ Nucleopolyhedrovirus
$(c)$ Root nodules	$(3)$ Phosphorus
$(d)$ Baculovirus	$(4)$ Bt-Cotton

Identify the colonies labelled as $A$ and $B$.

Which of the following is not used for the disinfection of drinking water?

Arrange the following in the decreasing order (most important first) of their importance,for the welfare of human society. Give reasons for your answer.
Biogas,Citric acid,Penicillin and Curd