Which of the following is a method of biological pest control?

Biological pest control involves using natural organisms to manage pest populations, making the act of releasing natural predators or parasites a key method in this approach. This method focuses on ecological balance and takes advantage of the natural relationships between species, where predators or parasites can help reduce pest numbers without the need for synthetic chemicals.

By introducing these natural enemies into an ecosystem, the existing pest population can be controlled more sustainably. This method is often more environmentally friendly compared to chemical approaches, as it minimizes the risk of harming non-target organisms and reduces the likelihood of pest resistance developing.

The other methods listed focus more on modifications or practices that do not specifically involve utilizing biological organisms for pest management. Planting genetically modified crops might enhance resistance to pests but does not directly involve biological control methods. Spraying chemical repellents employs synthetic solutions rather than natural relationships, and rotating crops primarily serves to disrupt pest life cycles without necessarily involving biological agents.