$Trichoderma harzianum$ has proved a useful microorganism for

Biological control methods adopted in agricultural pest control are based on:

Which is a bioinsecticide?

Bordeaux mixture can be prepared by mixing copper sulphate with:

Match the following columns and select the correct option:

Column $I$	Column $II$
$(a)$ Dragonflies	$(i)$ Biocontrol agents of several plant pathogens
$(b)$ Bacillus thuringiensis	$(ii)$ Get rid of aphids and mosquitoes
$(c)$ Glomus	$(iii)$ Narrow spectrum insecticidal applications
$(d)$ Baculoviruses	$(iv)$ Biocontrol agents of lepidopteran plant pests
	$(v)$ Absorb phosphorus from soil

Assertion $A$: The use of biocontrol agents prepared by microorganisms has become necessary as an alternative to chemical pesticides.
Reason $R$: The use of biological control agents helps maintain the balance of the ecosystem.
Which option is correct for Assertion $A$ and Reason $R$?