So, when gold was discovered in the West in 1849, he 23 thousands of others and rushed to California. 24 he planned to open a shop in San Francisco, he took many goods with him, 25 a large quantity of canvas.
答案：(B) Because
因果關係：「因為他計畫在舊金山開店，所以他帶了很多貨物」，Because 符合；Although（雖然，轉折）、If（如果，條件）、Unless（除非）都不符合這個因果邏輯。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
Although 在這裡有一點誘惑力，因為「帶很多貨物」聽起來像是件麻煩事，讀著讀著就想接一個轉折。但讓步要求前後互相牴觸，而「要開店」與「帶貨物」是同一個方向——開店本來就需要貨。
四個選項都是從屬連接詞，形態上刷不掉，可見這一格考的是前後兩件事的邏輯關係。前半是 he planned to open a shop in San Francisco（他打算在舊金山開一家店），後半是 he took many goods with him（他隨身帶了很多貨物）。打算開店是原因、帶貨物是結果，這是順向的因果，填 Because。順便一提，86 年第 21 題考的是完全一樣的判準（也是 Because 與 Although 二選一），兩題可以對照著看：只要前後兩件事同向，就不可能是讓步。
Although（雖然）：讓步，但前後同向。If（如果）：帶出假設，但他確實打算開店，不是假設。Unless（除非）：帶出排除性的條件（除非……否則……），本句沒有那個結構。
because ＋ 子句（因為）、although ＋ 子句（雖然）、plan to V（打算做……）、open a shop（開店）、take sth with sb（隨身帶著某物）、goods（貨物、商品）。
When Levi Strauss arrived in the United States from Bavaria, he was only seventeen, poor, and knew very 21 English. Like most immigrants, he was 22 a better life. So, when gold was discovered in the West in 1849, he 23 thousands of others and rushed to California.
24 he planned to open a shop in San Francisco, he took many goods with him, 25 a large quantity of canvas. He hoped to sell 26 as material for tents or wagon covers. Business, however, was not 27 he had expected.
28 , as he sat in a cafe in a small town, he had an idea. He saw a man with a hole in the leg of his trousers and 29 realized what Californians 30 for the rough work they were doing—good, strong trousers!