I had sat for hours in the classroom, reading a novel.

The weather has been cold so far this winter.

I had stayed in Beijing for three years by then.

Until then he had known nothing about it.

The boy told his mother that he had been ill since he came back from the school.

She had only been here for ten minutes when Jim came in.

When they got to the field, the football match had already started.

He said he had worked in that factory since 1949.

When I woke up, it had already stopped raining.

I had finished my homework before supper.

这些例句展示了过去完成时在不同句子结构中的使用，包括与时间状语连用、在从句中作为背景信息以及在叙述中的时间顺序。希望这些例句能帮助你更好地理解和运用过去完成时。