But no one could be expected to walk up 8, 10, or 30 flights of 28.
答案：(D) stairs
flights of stairs（一段段樓梯，flight 指樓層間連續的一段階梯）為固定搭配，表示沒有人能指望爬上8、10甚至30段樓梯（意指爬那麼多層樓）；attendants（服務員）／crews（全體工作人員）／planes（飛機）皆不符合 flights of 的搭配語意。
flight 這個字，你的印象大概只有「飛行、班機」，看到 flights of 就往飛機那邊想，於是挑了 planes 或 crews。
鑑別度高達 70，是本批最會分人的一題，在全庫也少見。關鍵在 flight 的另一個意思：a flight of stairs 指的是「一段樓梯」，也就是兩個樓層之間那一段連續的階梯，與飛行無關。整句是 no one could be expected to walk up 8, 10, or 30 flights of ______（不能指望有人爬八層、十層甚至三十層的______）。動詞是 walk up（往上走），走的當然是樓梯，所以填 stairs。填進去讀成 walk up 30 flights of stairs（爬三十層樓梯）。下一句說為了讓高樓更好進出而有了電梯，正是在說明為什麼需要電梯——因為樓梯爬不動。
planes（飛機）與 crews（機組人員）都是被 flight 的「班機」義帶著走的，形態吻合，容易被順手選走，但沒有人 walk up 一架飛機；attendants（服務員）同理，三個都與 walk up 這個動作接不上。
a flight of stairs（一段樓梯）、walk up（往上走、爬上）、take the stairs（走樓梯）、flight（飛行；班機；一段樓梯）、a flight attendant（空服員）、expect somebody to V（指望某人做某事）。
Science makes possible the use of new materials and new methods of producing objects. For example, some 20th-century chairs are made of steel and plastic. These materials, 24, were undreamed of in the 18th century. As new materials develop, one invention often 25 another.
Steel, for instance, was developed by engineers in the 19th century. 26 its strength, steel soon became a useful building material. 27 steel construction, buildings could then have a great many stories. But no one could be expected to walk up 8, 10, or 30 flights of 28.
Therefore, to make tall buildings more accessible to their users, the elevator 29. By providing much-needed space in a world 30 people, tall buildings have solved a great problem of the city and have completely changed our way of life.