paired fin

例句：

1. 1. The fish in the tank have pairs of fins that help them swim efficiently.
   鱼缸里的鱼有配对的鳍，这帮助它们高效游泳。
2. 2.The dolphins have a pair of fins on each side of their body.
   海豚每侧身体都有一对鳍。
3. 3.The shark has a pair of fins on its tail to propel itself through the water.
   鲨鱼在尾巴上有一对鳍，用来在水中推进。