stream gravity

例句：

1. 1.The stream of water flowed steadily through the valley.
   水流在山谷中稳定地流淌。
2. 2.The river is a constant source of life for the villagers.
   这条河流是村民们生命之源。
3. 3. The stream of tears ran down her cheeks as she cried.
   她哭泣时，泪水沿着脸颊流淌。