--- the farmers discovered the entrance to the secret cave in the valley?
--- Totally by chance.
A. When was it that
B. How was it that
C. How it was that
D. When it was that
网友回答
A. When was it that
(答案→)B. How was it that
C. How it was that
D. When it was that
解析：通过分析句子结构，可知这是一个特殊疑问句的强调句，基本结构是“特殊疑问词 + is/ was + it that……”因为把强调句的基本结构is/ was + it that去掉仍然是一个完整的句子，所以是强调句。