Climbing the most difficult mountains requires a very special mental condition. 21 the climber is doing something very difficult, everything that he or she sees, hears, or 22 must come together to help in the work of climbing.
答案：(B) Because
因果句：「因為攀岩者正在做很困難的事，所以……都必須配合」，Because 符合；Despite（儘管，介系詞用法不同）、Unless（除非）、Although（雖然，轉折）都不符合這裡的因果邏輯。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項的中文是「儘管、因為、除非、雖然」，只比意思會在 Because 與 Although 之間猶豫——「攀登很困難的山」聽起來確實像個阻礙，讀著讀著就想接一個轉折。這一格先用形態刷掉一個，再用語意分。
先看空格後面接什麼：the climber is doing something very difficult 是一個完整的子句，逗號之後 everything that he or she sees, hears, or feels must come together 又是完整的主要子句。所以空格要的是能帶出從屬子句的連接詞。Despite 先出局：它是介系詞，後面只能接名詞或動名詞（despite the difficulty、despite being tired），接不了一個完整的子句；真要接子句得寫成 despite the fact that。這一招是這一類題目的第一步——先看後面接的是名詞還是子句（同判準：88 年第 30 題的 In spite of 與 Consisting of）。剩下 Because、Unless、Although，用語意分：前半是「攀登者正在做一件很困難的事」，後半是「他所看到、聽到、感覺到的一切都必須整合起來幫助攀登」。困難是原因、全神貫注是結果，這是順向的因果，填 Because。
Although（雖然）：讓步要求前後互相牴觸，但「事情困難」與「必須全神貫注」是同一個方向。Unless（除非）：帶出一個排除性的條件，本句沒有那個結構。Despite：形態不合，接不了子句。
because ＋ 子句（因為）、because of ＋ 名詞（因為）、despite ＋ 名詞（儘管）、in spite of ＋ 名詞（儘管）、require sth（需要某物）、a special mental condition（特殊的心理狀態）。
Climbing the most difficult mountains requires a very special mental condition. 21 the climber is doing something very difficult, everything that he or she sees, hears, or 22 must come together to help in the work of climbing.
All of the parts of the body work together smoothly and quietly 23 each part feels what is happening in the other parts. There is no room for thinking about what time it is, or about how one looks. 24 thinking must focus on what is happening at that moment, and the mind and the body become one. Only by entering this quiet mental state 25 a climber really do his or her best.