问题补充：
---What made him so angry?
--- .
A. Because his son escaped from school
B. His son’s escaping from school
C. His son escaped from school
D. What his son escaped from school
答案：
A. Because his son escaped from school
(答案→)B. His son’s escaping from school
C. His son escaped from school
D. What his son escaped from school
解析：四个选项分别表示因为他的儿子逃学了,他儿子的逃学问题、他的儿子逃学了，选项D不和语法。其中选项B动词的现在分词，指的是他的儿子不止一次逃学，最符合题意，故选B。
