'সে যখন পড়ছিল, তখন আমি ঘুমাচ্ছিলাম।' Which one is the translation of this sentence?

উত্তর জানতে একটি অপশন বেছে নাও 👇

• কI was sleeping when he studied.
• খI was sleeping when he was studying.
• গI had been sleeping when he studied.
• ঘHe had been studying when I slept.