In this English error spotting and question tag item, identify the part that contains the error in: "You have been working very hard (A) for the past two years. (B) isn't it? (C) No Error (D)".

Introduction / Context:
This question tests your understanding of question tags, which are short questions added at the end of a sentence, usually to seek confirmation. The sentence is: "You have been working very hard (A) for the past two years. (B) isn't it? (C) No Error (D)". You must identify which segment contains a grammatical error. The key point here is forming the correct tag for a present perfect continuous sentence with "have".

Given Data / Assumptions:

• Main clause: "You have been working very hard for the past two years."
• Part (A): "You have been working very hard"
• Part (B): "for the past two years."
• Part (C): "isn't it?"
• Part (D): "No Error"
• The subject is "you", and the auxiliary verb in the main clause is "have".

Concept / Approach:
Question tags are formed by using the auxiliary or helping verb from the main clause, combined with the pronoun matching the subject. If the main clause is positive, the tag is usually negative, and vice versa. In "You have been working very hard", the auxiliary is "have" and the subject pronoun is "you". Therefore, the appropriate question tag should be "haven't you?" not "isn't it?" Using "is" and "it" would be correct only if the main clause had a corresponding form of "to be" and the subject "it". Thus, the error lies in part (C), where the wrong tag is used.

Step-by-Step Solution:
Step 1: Identify the tense and structure of the main clause: present perfect continuous "have been working".Step 2: Note the auxiliary verb "have" and subject "you".Step 3: Apply the standard rule: positive main clause → negative tag; auxiliary + subject pronoun.Step 4: Form the correct tag: "haven't you?" because "have" in the main clause corresponds to "haven't" in the negative tag, and "you" remains as "you".Step 5: Compare this with the given tag "isn't it?", which mismatches both the auxiliary and the pronoun, confirming that part (C) is incorrect.

Verification / Alternative check:
Rewrite the full sentence including the corrected tag: "You have been working very hard for the past two years, haven't you?" This sounds natural and fully accurate. If we try to keep "isn't it?", we get "You have been working very hard for the past two years, isn't it?", which is clearly wrong because the verb and pronoun in the tag do not refer back properly to the main clause. Parts (A) and (B) are otherwise correct and standard for describing an activity that has continued from the past up to the present.

Why Other Options Are Wrong:

• Option A (part A) is correct; "You have been working very hard" is a proper present perfect continuous statement.
• Option B (part B) is correct; "for the past two years" is a suitable time expression for this tense.
• Option D (No Error) cannot be right because we have identified a definite mistake in the question tag.

Common Pitfalls:
Many learners struggle with question tags because they try to memorise them as fixed phrases rather than deriving them from the main clause. The safest method is always to find the auxiliary verb in the main sentence and simply invert its polarity (positive/negative) in the tag, then match the pronoun to the subject. If you follow this systematic approach, you will avoid confusion between tags like "isn't it?", "don't you?", "haven't you?", and so on.

Final Answer:
The error is in part C. The correct question tag should be "haven't you?" instead of "isn't it?".