When they were first sold, aerosol insecticides were highly effective in killing flies and mosquitoes. Now, several decades later, a much smaller proportion of these insects die when sprayed. The reason fewer insects die when they are sprayed is that __________.
mosquitoes that survive spraying develop an immunity to the insecticide
mosquitoes are deliberately adapting themselves to this human-made change in the environment
the original spraying has caused a permanent mutation, giving the insects genetic resistance to the spray
None of the listed responses is correct.
many mosquitoes today are descendants of mosquitoes with insecticide-resistant characteristics