by-

例句：

1. 1.By the time we arrived, it was already dark.
   我们到达时天已经黑了。
2. 2.She decided to go home by bus.
   她决定坐公共汽车回家。
3. 3. He walked by the lake and saw a beautiful sunset.
   他走过湖边，看到了美丽的日落。