[文法] 想請教一題英文文法~

[causationist (Ringo)]

這題是這樣的
"Although"the scientific principles" on which"the telephone is based

had been "known" forty years earlier, it"had not been invented" by

Alexander Graham Bell until 1876.

"    "的部分要選出錯誤的
不好意思我沒有答案
我的直覺是第四個錯
但煩請高人告訴我錯在哪好嗎?

感激不盡

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推 linzh:was not invented