What kind of pollutants are described as living organisms that may cause harm?

The correct answer is pests because this term specifically refers to living organisms that can cause harm to humans, animals, or the environment. Pests include a wide range of organisms such as insects, rodents, and weeds that can damage crops, spread diseases, and negatively impact human health and well-being.

Understanding the concept of pests is critical in fields like agriculture and public health, where managing their populations is essential to prevent harm. Effective pest control measures aim to mitigate the risks associated with these organisms, making it clear why they fit the definition of pollutants that can cause harm.

The other terms mentioned do not appropriately describe living organisms in this context. Systemic poisons refer to substances that can cause harm to organisms through internal exposure, but they are typically chemical in nature rather than biological. Irritants are substances that provoke irritation upon contact, which can be chemicals or physical agents, rather than living organisms. Disinfection refers to the process of eliminating or reducing harmful microorganisms but does not apply to the definition of pollutants as living entities.