填空题

Where do pesticides (杀虫剂) fit into the picture of environmental disease We have seen that they now (36) soil, water, and food, that they have the power to make our streams fishless and our gardens and woodlands (37) and birdless. Man, however much he may like to pretend the contrary, is part of nature. Can he escape a pollution that is now so thoroughly (38) throughout our world
We know that even single (39) to these chemicals, if the amount is large enough, can cause extremely severe poisoning. But this is not the major problem. The sudden illness or death of farmers, farm workers and others exposed to (40) quantities of pesticides is very sad and should not occur. For the population as a whole, we must be more concerned with the delayed effects of absorbing small amounts of the pesticides that (41) pollute our world.
Responsible public health officials have pointed out that the biological effects of (42) are cumulative (累积的) over long periods of time, and that the danger to the individual may depend on the sum of the exposures received throughout his lifetime. For these very reasons the danger is easily (43) . It is human nature to shake off what may seem to us a (44) of future disaster. "Men are naturally most impressed by diseases which have obvious signs," says a wise physician, Dr Rene Dubos, "yet some of their worst enemies slowly approach them (45) ".
A．chemicals
B．obviously
C．threat
D．pollute
E．found
F．invisibly
G．touch
H．distributed
I．sufficient
J．avoided
K．exposure
L．ignored
M．silent
N．unnoticed
O．small