Much of the reef system is protected, 27 conservationists have long worried that not enough was being done to safeguard the area.
答案：(A) but
語意轉折：「這個珊瑚礁系統大部分受到保護，但是環保人士長期以來擔心保護不足夠」，but（但是）符合這個轉折；for（因為）、or（或者）、so（所以，這裡是轉折不是因果）都不合。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項都是對等連接詞，而這一段一直在介紹大堡礁，讀起來像在往下鋪陳，很容易挑 so。關鍵在前後兩半的方向是不是一致。
四個選項都是對等連接詞，可見這一格考的是前後兩半的關係。前半是 Much of the reef system is protected（大部分的礁區受到保護），後半是 conservationists have long worried that not enough was being done to safeguard the area（保育人士長期擔心保護做得不夠）。一邊說「有保護」、一邊說「擔心保護不夠」，方向相反，是轉折，填 but。再往後讀一句更確定：On April 3, 2010, their concerns came true.（2010 年四月三日，他們的擔憂成真。）——擔憂是真的有道理的，代表前面那個「有保護」確實不足以讓人放心。
so（所以）：因果。「受到保護，所以擔心保護不夠」自相矛盾。for（因為）：它引出的是前面那句話的理由，但「擔心保護不夠」不是「大部分受到保護」的原因。（for 的這個位置限制在題庫裡考過好幾次：83 年第 20 題、90 年第 21 題、91 年第 24 題。）or（或者）：提供另一個選擇，本句不是在二選一。
but（但是）、safeguard an area（保護某個區域）、a conservationist（保育人士）、come true（成真）、be protected（受到保護）、off the east coast（在東岸外海）。
Over the years, the Great Barrier Reef, off Australia's east coast, has grown to be 1,240 miles long. 26 up of 2,900 connected reefs, the area is home to thousands of plant and animal species. Much of the reef system is protected, 27 conservationists have long worried that not enough was being done to safeguard the area.
On April 3, 2010, their concerns came true. A cargo ship, Shen Neng 1, left Australia for China, carrying 65,000 tons of coal. Five hours into its 28 , the vessel strayed from its shipping lane. It plowed through a protected reef, destroying everything in its path. The damage covered an area as large as five football fields.
With more and more ships 29 the Great Barrier Reef, experts fear an even bigger accident is bound to happen. Fortunately, tougher rules are expected to 30 effect in July 2011. There are high hopes that these rules will prevent similar accidents from happening.