1 . 急流
◆ railway station(火车站) train station◆ rapids(急流) white water◆ rear〔bring up〕 (养育) raise
2 . 险滩
rank-size hierarchy 等级大小层系rapids急流;急滩;险滩ratio scale 比率量度
3 . 急流湍滩湍流
rapids急流;湍滩rapids急流湍滩湍流rare gas 稀有气体
4 . 湍滩
Rapidly Extensible Language 可快速扩充语言rapids急流;湍滩rapids急流湍滩湍流