Correct option is D
Explanation of the Correct Answer: · "Have not completed" (Present Perfect) changes to "had not completed" (Past Perfect) in reported speech.
· "Yet" remains the same.
· "The student admitted" suggests self-confession, so the verb remains unchanged.
Why Are the Other Options Incorrect? · (a) Hadn’t been able to complete → Incorrect; changes the meaning unnecessarily.
· (b) Hasn't been able to complete → Incorrect; incorrect verb tense.
· (c) Hasn’t completed → Incorrect; should be past perfect.
Thus, the correct answer is (d) The student admitted that he/she hadn’t completed the assignment yet.