The driver replied, "Sorry, sir. It's not really your 15. Today is my first day as a cab driver."
答案：(D) fault
fault（過錯）符合「這不是你的錯」的語意，呼應司機解釋自己今天第一天當計程車司機；matter／decision／trouble 均不符合此處語境。
四個選項都是名詞，都能接在 your 後面，你會憑中文挑一個。
空格落在司機說的話裡：Sorry, sir. It's not really your ______.（先生，抱歉，這其實不是你的______。）接著他解釋：今天是他第一天開計程車，過去二十五年開的是靈車——他在說明真正的原因在自己身上，所以前面那一句是在替乘客免責。It's not your fault（不是你的錯）是道歉場合的固定說法。填進去讀成 It's not really your fault。指考 100 年第 13 題考的 when the customer is at fault（當過錯在客戶那一方時）用的是同一個 fault，兩題可以擺在一起看：fault 講的就是過錯與責任歸屬。
matter 要在 What's the matter?（怎麼了）這種說法裡才這樣用，It's not your matter 不成立；decision（決定）與這裡的責任歸屬無關；trouble 雖然有 It's no trouble.（不麻煩）這個說法，但那是回應道謝、不是回應道歉，而且 your trouble 會變成「你的麻煩」。
It's not your fault.（不是你的錯）、at fault（有過失、該負責）、find fault with（挑剔、找碴）、What's the matter?（怎麼了）、It's no trouble.（不麻煩）、scare the living daylights out of somebody（把某人嚇得魂飛魄散）。
After a long day working in the office, Alexander hailed a taxi to take him home. Squeezing his body into the taxi, he noticed the shiny interior and the smell of brand new leather. After informing the driver of his 11, Alexander resorted to his reading of Dan Brown's intelligent thriller, The Da Vinci Code. Five minutes into the journey, he was on page 120: "…his Mona Lisa is neither male nor female…"
Suddenly, Alexander 12 and noticed that the driver had detoured from the familiar route. To redirect the driver, Alexander tapped him on the shoulder. Out of the blue, the driver screamed, lost control of the car, and almost hit a bus. The cab went up on the footpath and 13 stopped centimeters away from a shop window.
For a second, everything went quiet in the cab. Then the driver said, "Look, mate! Don't ever do that again. You scared the living daylights out of me!" Alexander apologized and said, "I didn't 14 that a little tap would scare you so much." The driver replied, "Sorry, sir. It's not really your 15. Today is my first day as a cab driver. I've been driving a funeral van for the last 25 years."