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질문할 때 예의를 지키시기 바랍니다.(빨리... 고수분만..... 이런 식의 요구는 자제 바랍니다.)
질문 내용 :

1. (A), (B), (C)의 각 네모 안에서 어법에 맞는 표현으로 가장 적절한 것은?
Aging is a result of the gradual failure of the body’s cells and organs to replace and repair (A) them / themselves. This is because there is a limit to the number of times that each cell can divide. As the body’s cells begin to near this limit, the rate at which they divide slows down. Sometimes the new cells that are produced have defects or do not carry out their usual task (B) effective / effectively. Organs can then begin to fail, tissues change in structure, and the chemical reactions that power the body (C) become / becoming less efficient. Sometimes the blood supply to the brain is not effective. The brain cells become short of oxygen and nutrients, leading to forgetfulness.
이건데요!(c)에서 답이 become 인데 왜 become 이고 become은 안되는지 모르겟어요 ~그리고 이것의 문제의도도요 ㅠㅠ