When asked to explain made his lessons so exciting, the teacher kept silent.
A. what it was that
B. that what it was
C. what was it that
D. that what was it
网友回答
(答案→)A. what it was that
B. that what it was
C. what was it that
D. that what was it
解析：句意：当被要求解释是什么让他的课使学生这么兴奋的时候，这个老师保持沉默。这句话中explain后面是宾语从句，宾语从句后缺成份，并且是做主语的物(做主语、宾语、表语，)，那要用what引导（如不缺成份用that），而且是强调句的特殊问句：is/was it…that…，那宾语从句中的疑问句要用陈述语序，因此是A。