草履虫

例句：

1. 1. The jellyfish is a common sight in the ocean.
   水母是海洋中常见的景象。
2. 2. The sea cucumber is a fascinating creature that can grow up to 30 feet long.
   海参是一种令人着迷的生物，可以长到30英尺长。
3. 3. The coral reef is an important habitat for many marine species.
   珊瑚礁是许多海洋物种的重要栖息地。