5. 글의 흐름으로 보아, 주어진 문장이 들어가기에 가장 적절한 곳을 고르시오.
Also, it has become difficult for companies to develop new pesticides, even those that can have major beneficial effects and few negative effects.
Simply maintaining yields at current levels often requires new cultivars and management methods, since pests and diseases continue to evolve, and aspects of the chemical, physical, and social environment can change over several decades. ( ① ) In the 1960s, many people considered pesticides to be mainly beneficial to mankind. ( ② ) Developing new, broadly effective, and persistent pesticides often was considered to be the best way to control pests on crop plants. ( ③ ) Since that time, it has become apparent that broadly effective pesticides can have harmful effects on beneficial insects, which can negate their effects in controlling pests, and that persistent pesticides can damage non-target organisms in the ecosystem, such as birds and people. ( ④ ) Very high costs are involved in following all of the procedures needed to gain government approval for new pesticides. ( ⑤ ) Consequently, more consideration is being given to other ways to manage pests, such as incorporating greater resistance to pests into cultivars by breeding and using other biological control methods.