Damselfish, for example, have been found to make sounds to scare off 12 fish and even divers.
答案：(C) threatening
【分詞作形容詞】現在分詞 threatening 修飾 fish，表示「具威脅性的魚」（主動意涵：這些魚對雀鯛構成威脅）。threatened 為過去分詞，語意變成「被威脅的魚」，不合文意；being threatened／being threatening 語法冗贅，不符英文慣用表達。
threatened 與 threatening 只差一個字尾，中文都能說成「威脅」，你會憑語感挑一個。
四個選項是同一個字 threaten 的不同形態排在一起，可見這一格考的是形態，要往前後找它該跟誰對齊。空格後面緊接著名詞 fish，所以空格填的是修飾 fish 的那個字。接著問方向：這些魚是「製造威脅的」還是「被威脅的」？雀鯛發出聲音是為了嚇跑對牠構成威脅的魚，那些魚是主動製造威脅的一方，所以用現在分詞 threatening。填進去讀成 scare off threatening fish（嚇跑具威脅性的魚）。國中的掛鉤是 a barking dog（會叫的狗，狗自己在叫）對 a broken window（破掉的窗戶，窗戶是被打破的），以及 interesting 與 interested 的分工。
threatened 是過去分詞，指「受到威脅的」，方向剛好相反——受威脅的是雀鯛自己，不是牠要嚇跑的那些魚；being threatened 與 being threatening 這兩個形態擺在名詞前面當修飾語不合英文習慣，being 只出現在被動進行式（is being threatened）或分詞構句裡。
threatening（具威脅性的）、be threatened（受到威脅）、scare off（嚇跑）、a barking dog（會叫的狗，現在分詞表主動）、a broken window（破掉的窗戶，過去分詞表被動）、interesting 與 interested（令人感興趣的／自己感到興趣的）。
The undersea world isn't as quiet as we thought, according to a New Zealand researcher. Fish can "talk" to each other and make a range of 11 by vibrating their swim bladder, an internal gas-filled organ used as a resonating chamber to produce or receive sound.
Fish are believed to speak to each other for a number of reasons, such as to attract mates, scare off predators, or give directions to other fish. Damselfish, for example, have been found to make sounds to scare off 12 fish and even divers. Another discovery about fish sounds is that not all fish are 13 "talkative." Some species talk a lot, while others don't. The gurnard species has a wide vocal repertoire and keeps up a constant chatter. Codfish, 14 , usually keep silent, except when they are laying eggs.
Any goldfish lover who hopes to strike up a conversation with their pet goldfish is 15 . Goldfish have excellent hearing, but they don't make any sound whatsoever. Their excellent hearing isn't associated with vocalization.