Which of the following is an example of herbicide?

The correct answer is A) Sodium chlorate. It is a non-selective herbicide that kills all green vegetation on the ground it is applied to, which is why it was used for total vegetation control on railway tracks, roadsides and industrial sites. Because it is a strong oxidiser and a fire hazard, its use is now restricted in many places.

• B) Potassium permanganate is a strong oxidising agent used as a disinfectant, antiseptic and in water treatment. It is not a herbicide.
• C) Bleaching powder (calcium hypochlorite mixture) is a chlorine-releasing disinfectant used for water chlorination and sanitation, and as a bleaching agent in textiles.
• D) Calcium carbonate is a liming material used to correct soil acidity, and it also works as an antacid. It has no herbicidal action.

The core concept is classification of agrochemicals: insecticides, fungicides, herbicides and rodenticides are regulated under the Insecticides Act, 1968, with registration handled by the CIB&RC. For Mains, this links to weed management and Integrated Pest Management, where herbicide misuse raises resistance and residue concerns.

Trap: Aspirants pick the chemical they know best from household or lab use, such as bleaching powder or permanganate, and forget that the question asks about agricultural function.