Their young captive 17 to be a mischievous boy.
答案：(C) turned out
【句型】turn out to be 字詞搭配「結果是」，表示「他們年輕的人質『結果』是個調皮搗蛋的男孩」；made believe（假裝）、got along（相處）、felt like（感覺想要）都不合。
turn out 在你腦中最熟的多半是「關燈」（turn out the lights）或「出席、到場」（Thousands of people turned out to welcome them.），比較少人第一時間想到它還有「結果是、原來是」這一義。另外 felt like 也很吸引人，因為你背過「想要」；但 feel like 後面接名詞或 V-ing，接不了 to be。
關鍵全在空格後面那兩個字 to be。四個選項裡只有 turn out 能接 to V — 劍橋詞典把 turn out 標為 B2，其中一義是「最後被發現是（往往出乎意料）」，句型就是 turn out to be + 名詞或形容詞。整句還原：Their young captive turned out to be a mischievous boy.（他們年幼的人質原來是個調皮搗蛋的孩子。）這個句型還有一個等值說法可以一起記，改寫題很好用：It turned out that their young captive was a mischievous boy. 也就是 turn out to be ＝ It turns out that…，兩種說法並存，意思相同。文意也支持：後面兩句 He viewed the kidnapping as a wonderful camping trip.（他把綁架當成一趟美好的露營之旅。）以及 He demanded that his kidnappers play tiring games with him.（他要求綁匪陪他玩累人的遊戲。）都在證明事情的發展出乎綁匪意料，這正是 turn out 的語感。順帶注意 demanded 後面的 play 沒有加 s，因為 demand、suggest、insist 這類表示「要求、建議」的動詞，帶出的 that 子句要用原形動詞。
make believe（假裝）後面接 that 子句（that 常省略），例 The children made believe they were pirates.（孩子們假裝自己是海盜。）get along（相處融洽）是不及物用法，要接對象時寫成 get along with sb，也接不了 to be。feel like（想要）後面只接名詞或 V-ing，例 I feel like going home.（我想回家。）
turn out to be（結果是、原來是）、It turns out that…（結果發現……）、turn out the lights（關燈）、turn out（出席、到場）、make believe（假裝）、get along with（與……相處融洽）、feel like + V-ing（想要做……）、demand that + 主詞 + 原形動詞（要求……）、view A as B（把 A 視為 B）。
Bill and Sam decided to kidnap the son of a banker to compensate for their business loss. They kidnapped the boy and hid him in a cave. They asked for a ransom of $2,000 to return the boy.
16 , their plan quickly got out of control. Their young captive 17 to be a mischievous boy. He viewed the kidnapping as a wonderful camping trip. He demanded that his kidnappers play tiring games with him, such as riding Bill as a horse for nine miles. Bill and Sam were soon desperate and decided to 18 the little terror. They lowered the price to $1,500.
Yet, knowing perfectly well 19 a troublemaker his son was, the father refused to give them any money. 20 , he asked the kidnappers to pay him $250 to take the boy back. To persuade the boy to return home, Bill and Sam had to tell him that his father was taking him bear-hunting. The kidnappers finally handed over the boy and $250 to the banker and fled town as quickly as they could.