Questionsare based on the following passage. Where do pesticides （杀虫剂） fit into the picture of environmental disease? We have seen thatthey now（36）soil， water， and food， that they have the power to make our streams fishless andour gardens and woodlands（37）and birdless. Man， however much he may like to pretend thecontrary， is part of nature. Can he escape a pollution that is now so thoroughly（38）throughoutour world? We know that even single（39）to these chemicals， if the amount is large enough， cancause extremely severe poisoning. But this is not the major problem. The sudden illnessor death of farmers， farm workers and others exposed to（40）quantities of pesticides isvery sad and should not occur. For the population as a whole， we must be more concernedwith the delayed effects of absorbing small amounts of the pesticides that（41）pollute ourworld. Responsible public health officials have pointed out that the biological effects of（42）arecumulative （累积的） over long periods of time， and that the er to the individual may dependon the sum of the exposures received throughout his lifetime. For these very reasons the er iseasily（43）. It is human nature to shake off what may seem to us a（44）of future disaster. 'Menare naturally most impressed by diseases which have obvious signs，' says a wise physician， Dr ReneDubos， 'yet some of their worst enemies slowly approach them（45）'.