潮汐池里的動物: mussel,barnacle, sea anemone,sea spider,octopus, sea cucumber, abalone, hermit crab, sea star 潮汐池的危險: the way the water moves,drying out 海星的身體部位: spiny skin,eyespots,tube feet, arms,mouth 指示代詞的用法，例如: this,these 副詞的用法，例如: safely 介詞的用法，例如: in,on,at, through 情態動詞的用法，例如: can,must, may 并列句，例如: A few have long arms, and others have frills. 定語從句，例如: Lots of seaweeds have anchors that hold them in place. 特殊疑問句，例如: Who lives here?