【rick325】評論
They had to learn from their own mistakes, which __25__ some their lives, and almost all suffered light or severe injuries. 從上文得知他們必須從自己的錯誤中學習，那這邊的which指的就是"學習"，那學習_______他們其中一些人的生命，甚至是幾乎他們的每人都有過大大小小的受傷，這邊的空格最適合的邊是有著消耗、花費的Cost