A few hours later, 18 traveler came down the road.
答案：(D) another
語意「幾小時後，『另一位』旅人沿路而來」，another（另一位，不特指的另一個）符合；a（不太符合「再一個」的強調語意）、the（定冠詞，這是新出現的人物不是特指）、other（需要接複數名詞，不能直接接單數traveler）都不合。
你多半覺得 a traveler 也通——「幾小時後，一位旅人沿路而來」，中文唸起來完全沒問題，於是選了 a。這是本題最大的陷阱：a 在文法上不算錯，卻漏掉了「又來了一個」這層意思。另一種可能是看到「其他的」就直接抓 other。
先用文法刷掉一半。other 後面要接複數名詞或不可數名詞（other travelers、other information），要接單數可數名詞就必須用 another（an 與 other 合起來）或 the other。題目裡的 traveler 是單數，other 直接出局。這是國中就學過的：I have two pens. One is red; the other is blue.（兩支中的另一支，特指）對照 I don't like this one. Show me another.（許多之中的另一個，不特指）。再從語境決定要 a 還是 another。前面已經出現過第一位旅人（a traveler asked him...），現在來的是同類型的第二位，屬於「再一個」，這正是 another 的功能。「重複」是貫串整篇的主軸：這位旅人 asked Aesop the same question、伊索 made the same request，下一格填的又是 Again，全篇都在講同一件事再上演一次。用 a 只是單純引介一個新人物，接不上這條線。the 更不行：the 表示雙方都知道指的是哪一位，這位旅人第一次出場，讀的人無從指認。
a：文法通但語意弱，讀不出「又一位」的重複感。the：定冠詞用於已知或特指的對象，此處是新登場的人物。other：後面不能直接接單數可數名詞。
another（再一個、另一個，後面接單數名詞）、the other（兩者中的另一個）、the others（其餘的全部）、one after another（一個接一個）、another two weeks（再兩個星期）、one another（彼此、互相）。
Aesop, the Greek writer of fables, was sitting by the roadside one day when a traveler asked him what sort of people lived in Athens. Aesop replied, "Tell me where you come from and what sort of people live there, and I'll tell you what sort of people you'll find in Athens." 16 , the man answered, "I come from Argos, and there the people are all friendly, generous, and warm-hearted. I love them." 17 this, Aesop answered, "I'm happy to tell you, my dear friend, that you'll find the people of Athens much the same."
A few hours later, 18 traveler came down the road. He too stopped and asked Aesop the same question. 19 , Aesop made the same request. But frowning, the man answered, "I'm from Argos and there the people are unfriendly, 20 , and vicious. They're thieves and murderers, all of them." "Well, I'm afraid you'll find the people of Athens much the same," replied Aesop.