The mark of heroes is not necessarily the result of their action, but 24 they are willing to do for others and for their chosen cause. 25 they fail, their determination lives on for others to follow.
答案：(B) Even if
【句型】even if 字詞搭配「即使」，表示「即使他們失敗了，他們的決心依然能激勵他人」；Not until（直到……才）、As if（彷彿）、No sooner than（不是標準搭配，需要完整倒裝結構）都不合。
Not until 與 No sooner than 這兩個選項長得很有氣勢，你可能會被它們吸走。但這兩個一放到句首，句子的形態就必須跟著改變——它們有很硬的文法條件，先檢查條件過不過，比慢慢想語意快得多。
先看句子的形態：空格後面是 ___ they fail, their determination lives on for others to follow，主要子句 their determination lives on 是正常語序，主詞在前、動詞在後，沒有倒裝。這一點等一下會一口氣刷掉兩個選項。確定形態沒問題之後再看語意：Even if 是「即使」，用來讓步——即使失敗了，決心依然延續下去，正好接上最後一句 The glory lies not in the achievement but in the sacrifice（榮耀不在成就，而在犧牲）。整段的意思是「失敗與否不影響決心的價值」，讓步關係完全吻合。
Not until 放在句首時，主要子句一定要倒裝，也就是把助動詞搬到主詞前面：Not until they fail does their determination live on...。原句沒有倒裝，Not until 立刻出局。這裡說的倒裝專指主詞與助動詞位置對調，跟 Not only had he... 是同一族。No sooner 的正確形態是 no sooner...than...，同樣要倒裝、還要配過去完成式：No sooner had they failed than...。選項寫成 No sooner than 已經把中間該有的東西砍掉了，形態本身就不完整。這兩個選項都不必想語意，光看主要子句沒倒裝就能刷掉。As if 是「彷彿、好像」，形態上沒問題，但它用來打比方，而這裡說「他們的決心延續下去讓別人跟隨」是真的在發生，不是比喻，語意上不合。順便分清楚 even if 與 even though：even if 講的是還沒發生、帶假設意味的（Even if it rains, we will go.）；even though 講的是已經是事實的（Even though it was raining, we went.）。
even if（即使、就算）、even though（雖然、儘管）、not until...（直到……才）、no sooner...than...（一……就）、as if（彷彿、好像）、live on（繼續存在、延續下去）。
There are two kinds of heroes: heroes who shine in the face of great danger, who perform an 21 act in a difficult situation, and heroes who live an ordinary life like us, who do their work 22 by many of us, but who 23 a difference in the lives of others.
Heroes are selfless people who perform extraordinary acts. The mark of heroes is not necessarily the result of their action, but 24 they are willing to do for others and for their chosen cause. 25 they fail, their determination lives on for others to follow. The glory lies not in the achievement but in the sacrifice.