It was created 18 the format of XYX, with X being any number between 2-9 and Y being either 1 or 0.
答案：(D) in
in the format of 是「以…的格式」，in 表示「以某種形式、方式」；for（為了）、as（作為）、by（藉由某種方法）語意都不合。
created 後面接 in，你可能會覺得怪：被創造出來的東西不是「在」格式裡面。所以手會伸向 as——「被創造成 XYX 這種格式」，中文聽起來最像。你看出這一格要交代「長成什麼樣子」，方向對了，錯在 in 有一格用法沒進到記憶裡：in 加名詞可以表示「以某種形式、用某種方式」，跟「在裡面」無關。
先看被創造的是什麼。主詞 It 指的是前面那個 area code（區碼），XYX 是它的排列樣式，不是它本身。所以這一格要接的是「以某種樣式呈現」，正是 in the format of（以…的格式）。這一格屬於 in 的「方式與形式」那一組，一起記最有效率：in English（用英文）、in ink（用墨水）、in cash（付現）、in capital letters（用大寫）、in the form of（以…的形式）。format 這個字也可以從字根回推：form（形狀、形式）長出來的一整家人還有 formal（正式的）、formula（公式）、transform（改變形態）、uniform（同一種形式，也就是制服）。一句記完：The shop printed its coupons in the format of a postcard, so customers could mail one home while waiting in line.（那家店把折價券印成明信片的形式，排隊的顧客可以順手寄一張回家。）〔情境取材自 107 學測作文題：排隊嘗鮮〕
as（作為）：會把區碼說成格式本身，但被創造的是區碼，格式只是它的樣子。for（為了）：帶出目的，格式不是目的。by（藉由）：帶出方法或手段，格式是結果不是手段。三個選項的中文都常見，差別只在這一格要的是「形式」，而形式這一格固定歸 in。這裡不必記反義，記同義就夠：in the format of 等於 in the form of，也等於 following the pattern of。
in the format of（以…的格式）、in the form of（以…的形式）、in cash（以現金）、in capital letters（用大寫字母）、in its entirety（完整地、一字不漏地）、be based in（位於、設於）、be charged at a lower rate（以較低費率計費）、area code（區碼）。
An area code is a section of a telephone number which generally represents the geographical area that the phone receiving the call is based in. It is the two or three digits just before the local number. If the number 16 is in the same area as the number making the call, an area code usually doesn't need to be dialed. The local number, 17 , must always be dialed in its entirety.
The area code was introduced in the United States in 1947. It was created 18 the format of XYX, with X being any number between 2-9 and Y being either 1 or 0. Cities and areas with higher populations would have a smaller first and third digit, and 1 as the center digit. New York, being the largest city in the United States, was 19 the 212 area code, followed by Los Angeles at 213.
In countries other than the United States and Canada, the area code generally determines the 20 of a call. Calls within an area code and often a small group of neighboring area codes are normally charged at a lower rate than outside the area code.