Question

Which pesticide is a herbicide?
A) Malathion
B) Lindane
C) BHC
D) $2,4{\text{ - D}}$

Answer 1

Pesticides are substances which can be used to destroy pests. A pesticide can be a chemical or it can be a biological agent such as virus, bacterium, antimicrobial or a disinfectant. It is commonly used to eradicate pests that can damage crops and livestock and reduce productivity of crops.

Complete answer:
Pesticides are classified based on the type of pest they kill.
Insecticides are effective against insects
Herbicides are effective against plants
Rodenticides are effective against rodents (rats & mice)
Bactericides are effective against bacteria
Fungicides are effective against fungi
Larvicides are effective against larvae.
Another type of classification is based on how biodegradable they are classified as biodegradable and persistent.
Biodegradable are those which can be broken down by microbes and other living beings into harmless compounds. Persistent ones have long half lives and it takes years or months to break down.
$2,4{\text{ - Dichloro Phenoxy Acetic Acid}}$ is a systemic herbicide which affects dicot weeds without affecting monocot cereals. It is also known by the name trinoxol. It is the most widely used and commonly available herbicide. It can mimic the action of plant hormone auxin which leads to unpredictable growth and eventually death.
Malathion is a man-made organophosphate insecticide that is used to control mosquitoes.
Lindane is gamma hexachlorocyclohexane insecticide which can be used for agricultural purposes as well as pharmaceutical treatment i.e., for treatment for lice and scabies.
BHC (β-Hexachlorocyclohexane) is another name for Lindane.

So, the correct answer is Option D.

Notes:
Pesticides are also classified based on the way they are produced from or based on their chemical forms.
Organophosphate: Most organophosphates are insect sprays which influence the sensory system by disturbing the catalyst that manages a synapse.
Carbamates: Like the organophosphorus pesticides, the carbamate pesticides additionally influence the sensory system by upsetting a chemical that directs the synapse.
Organochlorine insecticides: They were regularly utilized before, yet now numerous nations have eliminated them from their market because of their negative environmental impact (e.g., DDT, chlordane, and toxaphene).
Pyrethroid: These are a manufactured form of pyrethrin found in Chrysanthemum(Flower)
Sulfonylurea herbicides: The sulfonylureas herbicides have been popularized for weed control, for example, pyrithiobac-sodium, cyclosulfamuron.
Biopesticides: The biopesticides are specific kinds of pesticides derived from natural sources such as animals, plants, microorganisms, and certain minerals.