✔ Correct Answer: A. I don't know why he left early.
The correct answer to the question “Find out the correct sentence: I don't know why he left early., I don't know why did he leave early., I need not to know why he left early., I should know why was he leaving early.” is I don't know why he left early.. This question belongs to Grammar Concepts & Terms in English. Practice the related questions below to master this topic for your FPSC, PPSC and NTS tests.