我在听讲座时渐渐睡着了。
I ___drifted ___off while listening to the lecture.
飞机起飞后不久,他就渐渐睡着了。
He ___drifted ___off shortly after the airplane took off.
电影太无聊了,她看到一半就渐渐睡着了。
The movie was so boring that she ___drifted ___off halfway through.