Which of the following is classified as a pesticide?

Glyphosate is classified as a pesticide because it is a broad-spectrum herbicide commonly used to kill weeds and grasses that compete with crops. It works by inhibiting a specific enzyme pathway found in plants and some microorganisms, which is not present in animals. This selective action makes glyphosate an essential tool in agricultural practices to enhance crop yields and manage weed populations effectively.

The other substances listed do not fall under the category of pesticides. Potassium is a chemical element essential for plant nutrition, utilized primarily as a fertilizer. Ricin is a highly toxic protein derived from the castor bean plant and does not serve a pest control purpose. Rattlesnake venom is a mixture of enzymes and proteins used for predation and defense, but it is not employed as a pesticide in agricultural settings. Hence, glyphosate is the only option that functions as a pesticide.