Solution: The sentence in question is: "He did not knew that the train had already left." The error is found in the phrase "not knew."
Explanation: In English, when forming the past tense in negative sentences with the auxiliary verb "did," the main verb should be in its base form. Therefore, "knew" should be changed to "know" as "did" already indicates past tense. The correct phrase should be "did not know."
Corrected Sentence: He did not know that the train had already left.
Identify the part of the sentence that contains an error:
"Neither the manager nor the employees ___ willing to accept the new policy."