In the 1930s, people started to try DDT invented by the Swiss chemist Mller. Just as people were fortunate to find high-efficiency pesticides that put the pests dead, the natural enemies of the Beijing insects were almost extinct. At the same time, the residual poison of DDT could accumulate for a long time. Has caused endless calamities in the world. The reason explained in the above paragraph is:. ['If used improperly, the application of efficient pesticides will also cause worldwide pollution.', 'DDT has proven to be a harmful and harmful pesticide to humans.', 'Excessive application of high-efficiency pesticides can also cause devastating disasters to natural enemies of pests.', 'Some scientific achievements are "double-edged swords", and their use needs to be cautious.']