◇ Reduced Relative Clauses
關係子句簡化為分詞片語
關係代名詞省略時，要注意的事情。我們來看看句子：Though nobody knew it at the time, these were the signs of a dangerous immune response unfolding inside his body. 這句話後半句乍看有兩個動詞：were 和 unfolding。依句意 （雖然當時都沒人知道，但這是那些症狀表示一個嚴重的免疫反應在他體內展開。） 和上下文來看，可以發現 were 的動詞主體是 these， 而 unfolding 的主體是 a dangerous immune response 。所以其實這句原本應該是：Though nobody knew it at the time, these were the signs of a dangerous immune response that/which unfolds inside his body. 當關係代名詞作為關係子句中的主詞，關係代名詞 that/which 省略後，其後的動詞型態也要有所變化，變成分詞。至於是要變成現在分詞（Ving）還是過去分詞（V.pp），就要看該動詞是否是被動態。如果不是被動的話，該動詞改為Ving；如果是被動，則保留Vpp的型態。 我們再來看看其他例句：
Example：
1. The girl who sang tonight is my idol. (The girl singing tonight is my idol.)
今晚唱歌的那個女孩是我的偶像。（sing 的主詞是 the girl，女孩唱歌的行為不是被動）
2. Cindy wants to talk with the man who is dressed in a brand-name suit. (Cindy wants to take with the man dressed in a brand-name suit.)
Cindy 想跟那個穿名牌西裝的男生講話。（be dressed in 本身就是被動語態的片語，故 who is dressed in 的關係代名詞 who 省略，剩下來的動詞 is dressed 作變化，留下 Vpp，is也省略後改為 Cindy wants to take with the man dressed in a brand-name suit.）
3. The dog that is running around in the park is my pet. (The dog running around in the park is my pet.)
那隻在公園裡跑來跑去的狗是我的寵物。（run around 的主詞是 the dog，跑的行為並不是被動，所以改成The dog running around in the park is my pet.）