다음 글에서 필자의 심경이 변하는 것을 알려주는 단서로 부적절 한 것은?

My electric wheelchair was ①a tremendous source of freedom for me while I was growing up. It gave me the independence to move about in ways that I was not able to do under my own power. ②However, as ③I became older, I realized that the electric wheelchair that had once given me so much freedom was quickly becoming ④an obstacle of confinement. I felt that I was an independent person except for the fact that I was limited by my dependency on my electric wheelchair. ⑤The very thought of being dependent onanything for the rest of my life bothered me.

필자의 심경이 변하는 것을 알려주는 단서이기 때문에
이전의 wheelchair 에 대한 심경 - a tremendous source of freedom
생각이 반대로 바뀌었다는 것을 알려주는 - However
나이를 들어가면서 변했다는 것을 알려주는 - I became older
나이가 든 후의 wheelchair 에 대한 심경 - an obstacle of confinement
그래서 느끼는 심경 - The very thought ~ bothered me

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