Biological control in agriculture refers to the use of natural enemies of pests to control their population. Option 1, antibiotics, is incorrect as antibiotics are substances used to kill or inhibit the growth of bacteria, not pests. Option 2, biofertilizers, is also incorrect as biofertilizers are used to enhance plant growth and development, not to control pests. Option 3, pesticides, is also incorrect as pesticides are chemical substances used to kill or repel pests, which is opposite to the idea of biological control. Option 4, natural enemies of pests, is the correct answer. Natural enemies, such as predators, parasites, and pathogens, are used to control pest populations in an environmentally friendly and sustainable way. By releasing these natural enemies into the agricultural environment, they feed on or infect pests, reducing their populations and preventing damage to crops. Biological control is considered a safe and effective alternative to chemical pesticides, as it minimizes negative impacts on the environment and human health.