Trade is driven by different production costs in different countries, making 26 cheaper for some countries to import goods rather than make them.
答案：(D) it
虛受詞 it，代替後面的真正受詞 to import goods（使進口貨物變得更便宜這件事）；them（不是指代特定的複數名詞）、such、what 都不合。
你熟的是「虛主詞 it」：It is cheaper to import goods than to make them.（進口貨物比自己生產便宜。）這個句型國中就見過。但本題的 it 出現在 making 後面，位置是受詞不是主詞，就不會聯想到「虛主詞」 — 答對率只有 46%。
這是一句分詞構句，先還原成完整子句，還原完就通了。原句尾巴是 …, making {26} cheaper for some countries to import goods rather than make them，還原成 …, and this makes it cheaper for some countries to import goods rather than make them.（……而這使得某些國家進口貨物比自己生產便宜。）接著把 it 代表的內容放回原位試試看：makes to import goods cheaper for some countries — 動詞 make 後面卡著一長串不定詞當受詞，英文不接受這種頭重腳輕的排法，所以先擺一個 it 把受詞的位子占住，真正的內容 to import goods 移到句尾。劍橋 English Grammar Today 在「It」條把這種 it 稱為「空的（empty）受詞」，並說明它的功能是「預示（anticipate）」後面真正的主詞或受詞；台灣課本習慣叫「虛主詞、虛受詞」，講的是同一件事。這個句型請整組記起來：make、find、think、consider + it + 形容詞 + to V，例 I find it difficult to talk to her.（我覺得跟她講話很吃力。）跟本題結構一模一樣。至於為什麼連高分群考生也會在這一格失手（本題鑑別度偏低，D 值 31）：難處不在英文，而在「看不見」。逗號後面是分詞構句，主詞被省略；讀到 making 之前，你已經先消化了 Trade is driven by different production costs in different countries 這一長串經濟概念，注意力全花在讀懂內容上，很容易把 making it cheaper 整團當成語感滑過去，沒有停下來問一句「這個 it 指的是誰」。答錯的人多半不是不懂虛受詞，而是根本沒察覺這裡在考虛受詞。看到分詞構句就先還原成完整子句，用意正是逼自己把每個成分看清楚。
them 是代名詞，必須有明確的複數先行詞；句中最近的複數名詞是 countries 和 costs，代進去都講不通（而且句尾的 them 已經另有所指，指的是 goods）。such 不能單獨擺在這個位置當受詞。what 是關係詞或疑問詞，會帶出一整個子句，但後面的 cheaper for some countries to import goods 不是 what 帶得動的結構。
make it + 形容詞 + to V（使做某事變得如何）、find it difficult to V（覺得做……很困難）、think it necessary to V（認為有必要做……）、rather than（而不是）、be driven by（受……驅動、由……推動）、production costs（生產成本）、a comparative advantage（比較利益）。
International trade is the exchange of goods and services between countries. Trade is driven by different production costs in different countries, making 26 cheaper for some countries to import goods rather than make them. A country is said to have a comparative advantage over another when it can produce a commodity more cheaply. This comparative advantage is 27 by key factors of production such as land, capital, and labor.
While international trade has long been conducted in history, its economic, social, and political importance has been 28 in recent centuries. During the 1990s, international trade grew by nearly 8.6 each year. In the year 1990 alone, the growth in trade in services was as high as 19. Today, all countries are involved in, and to varying degrees dependent on, trade with other countries.
29 international trade, nations would be limited to the goods and services produced within their own borders. Trade is certainly a main 30 force for globalization. It is also the subject of many international agreements that aim to govern and facilitate international trade, such as those negotiated through the World Trade Organization (WTO).