Farmers often spray crops with chemical pesticides .In the short term this is a completely effective way of getting rid of pests. However, these pesticides often poison other living things and pollute the environment. Another way of controlling pests is to find animals that will eat them and introduce it to the crop growing area. A predator will keep pests under control naturally, although this method will not eliminate the pests completely. This method, known as biological pest control, causes virtually no damage to the environment. So, where possible, biological pest control should be used in preference to chemical pesticides.
Which one of the following is an underlying assumption of the above argument?