His father, 19 always hoped that he would get a PhD and become a professor, 20 with a scoff: “What is all this nonsense?!”
答案：(A) who
關係代名詞 who 引導非限定關係子句，修飾先行詞 His father（他的父親一直希望他能拿到博士學位）；while（連接詞不是關係代名詞）、that（非限定關係子句通常不用that）、when（不修飾人）都不合。
被一對逗號夾住的那一段常常被跳過不讀，於是 His father 和第 20 格之間隔了一長串，等到要填第 20 格時已經忘了主詞是誰。這兩格其實是一組：先認出 who ... professor 只是插進來補充說明父親的，才看得出來第 20 格才是整句真正的主要動詞。
先看四個選項的共同點：who、while、that、when 都是用來把兩段話接起來的詞，沒有一個在考單字意思，可見這一格問的是「後面那個子句要用什麼接上來」。（同卷第 21 題也是四個 wh- 詞，但那一格是間接問句；兩者的分辨方法寫在第 21 題。）空格後面直接就是動詞 always hoped，前面缺一個主詞，所以空格要填的是能兼當主詞的關係代名詞，而先行詞 His father 是人，用 who。還原成兩句就一目了然：His father always hoped that he would get a PhD and become a professor. ＋ His father reacted with a scoff.，把重複的 His father 換成 who，再用一對逗號把它嵌回去。這種用逗號夾住、只是補充說明的關係子句叫非限定關係子句。
that：非限定關係子句不用 that（劍橋 English Grammar Today 的 relative clauses 條目），看到逗號就可以先把 that 刷掉。while、when：兩個都是連接詞，後面要接一個主詞齊全的子句，但這裡動詞 hoped 前面正好缺主詞；而且 when 用來接時間，不能拿來指人。
hope that 子句（希望……）、get a PhD（取得博士學位）、major in（主修）、go on tour（巡迴演出）、exhaust oneself（使自己筋疲力盡）、it turns out that（結果是……）。
Experts say that creativity by definition means going against the tradition and breaking the rules. To be creative, you must dare 16, and courageously express your own outlook and 17 what makes you unique. But does our society encourage children to break the rules? I'm afraid the answer is no.
The famous film director Ang Lee recalls his father's disappointment with him when he was young. 18 a small child, he would pick up a broom and pretend to be playing guitar for the entertainment of family guests. Then, when he was studying film in college, he would exhaust himself just for a performance tour. His father, 19 always hoped that he would get a PhD and become a professor, 20 with a scoff: "What is all this nonsense?!"
But it later turned out that it was exactly his courage to "rebel" and to express his own ideas that marks his films with distinct creativity.