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.
答案：(A) crowded with
a world crowded with people（擁擠著人群的世界）表示人口稠密的世界，摩天大樓提供急需的空間；jammed on／growing up／increasing by 均不符合此處語意搭配。
四個選項都是兩個字的組合，你會憑中文挑一個；而且 growing up 與 increasing by 看起來都與「人變多」有關，很容易把你吸走。
答對率四成二。先看結構：空格前是 a world（一個世界），後面是 people（人）。空格這一串是掛在 a world 後面補充說明它是什麼樣的世界，所以要的是一個能擺在名詞後面當修飾語、而且後面還能接 people 的形式。be crowded with 是「擠滿了……」，把 be 動詞拿掉、只留過去分詞片語 crowded with people 掛在名詞後面，就是「一個擠滿人的世界」。填進去讀成 in a world crowded with people（在一個擠滿人的世界裡）。這與 a book written by him（他寫的書）是同一個結構：過去分詞片語擺在名詞後面當修飾語。
jammed on 的成組說法是 jam on the brakes（猛踩煞車），後面接的不是人；growing up（成長）是不及物的，後面不能直接接 people；increasing by 後面接的是增加的幅度（increasing by 5 percent），不是增加的東西。
be crowded with（擠滿了）、be filled with（充滿了）、be packed with（塞滿了）、過去分詞片語當名詞的後位修飾語（例如 a book written by him 他寫的書）、jam on the brakes（猛踩煞車）、much-needed space（亟需的空間）。
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.