Identify the part of the sentence that contains a grammatical error: I had not completed my English homework (1) / so I thought I was done with when the (2) / teacher asked me to hand it in. (3) / No error (4).

Introduction / Context:
This error-spotting question checks your ability to notice missing words and incomplete phrases in an otherwise simple sentence about homework. The sentence is divided into four parts, and you must determine which part contains the grammatical error. The situation describes a student who had not completed homework and was then surprised when the teacher asked for it.

Given Data / Assumptions:

• Part (1): “I had not completed my English homework”.
• Part (2): “so I thought I was done with when the”.
• Part (3): “teacher asked me to hand it in.”
• Part (4): “No error”.
• We assume standard spoken and written English usage.

Concept / Approach:
The key grammar concept is that the expression “to be done with something” always requires an object, usually represented by a pronoun like “it”. Saying “I thought I was done with” without an object makes the sentence incomplete. Therefore, the error lies in the phrase “I was done with when the”, which is missing “it”.

Step-by-Step Solution:
Read Part (1): “I had not completed my English homework” – this is a correct past perfect statement.Read Part (2): “so I thought I was done with when the” – this feels incomplete and awkward.Recognize that the natural phrase is “I thought I was done with it when the teacher…”Read Part (3): “teacher asked me to hand it in.” – this is grammatically correct.Therefore, the error is clearly in Part (2), where the object “it” is missing after “done with”.

Verification / Alternative check:
Insert the missing word and read the entire sentence: “I had not completed my English homework, so I thought I was done with it when the teacher asked me to hand it in.” Now the sentence is grammatically correct and the meaning is clear: the student wrongly assumed that no one would ask for the homework.

Why Other Options Are Wrong:
Part (1) correctly uses the past perfect tense to show an action completed before another past event. Part (3) has proper word order and prepositions. Since only Part (2) is incomplete, options “1”, “3” and “4” are incorrect. “No error (4)” cannot be correct because we clearly identify a missing word in Part (2).

Common Pitfalls:
Students sometimes focus only on verb tense and ignore small but essential words like pronouns. Expressions such as “be done with something” always need an object; forgetting this object is a common mistake in spoken English and therefore appears frequently in competitive exam questions.

Final Answer:
The part of the sentence that contains the error is 2.