The more pesticides are used, the more resistant the insects become so the more pesticides have to be used. It's a vicious circle.杀虫剂用得越多，昆虫的抗药力就变得越强，于是又要用更多的杀虫剂。这是一个恶性循环。He refused medication, and, when it was forced on him, his body rejected it.他拒绝药疗，而当他被迫用药时，他的身体又产生了抗药反应。Overuse of antibiotics may foster the spread of drug-resistant bacteria.滥用抗生素可能助长抗药细菌的扩散。