【推荐1】我正在街上走，突然看到一位老人从自行车上摔了下来。(sb. was/were doing ... when ... )
I __________ I suddenly saw an old man fall off his bicycle.

【推荐2】她沿着河堤边走边唱流行歌曲。
______along the river bank, she was singing a pop song.

【推荐3】He walked so fast that I couldn't catch up with him.
→So fast ________ I couldn't catch up with him.

【推荐2】我记得非常清楚，以前，湛蓝的天空，鸟儿的歌唱、月光和鲜花，从未令我心迷神往。
I can well remember that there was a time            a deep blue sky, the song of the birds, moonlight and flowers could never have kept me spellbound.

【推荐3】我正在家看电视，这时突然有人敲门。
I ________ ________ ________ ________someone knocked at the door.

【推荐1】The boy ________ ________   when he fell off his bike.       那个小孩正骑着车，就在这时，摔了下来。

【推荐2】我们正要离开教室，这时我们的班主任走了进来。(when)
We ________ our head teacher came in.