Which of the following best defines a pesticide?

The definition of a pesticide is encapsulated in the notion of preventing or mitigating pests. Pesticides are substances specifically formulated to control harmful organisms that can damage crops, livestock, or stored products. This includes a variety of chemicals that target insects, weeds, fungi, and other pests, thereby playing a crucial role in agricultural productivity and protecting food supplies.

The other choices provided are centered around different functions or categories of substances. The first option refers to substances aimed at promoting plant growth, which aligns more closely with fertilizers than with pesticides. The second option incorrectly suggests that chemicals can have no side effects, which is not accurate in the context of pesticides, as many can have unintended consequences. Lastly, the fourth choice relates to organic fertilizers, which are not pesticides but rather nutrients for enhancing plant growth. Thus, the focus on preventing or mitigating pests captures the essence of what a pesticide is and emphasizes its protective role in agriculture.