问题补充：
When I try to find that prevent so many people from taking part in the program, it seems to me that there are two main causes.
A. why it does
B. what it does
C. what it is
D. why it is
答案：
A. why it does
B. what it does
(答案→)C. what it is
D. why it is
解析：主要测试宾语从句。首先分析句子结构以及答案可知出题人只不过把宾语从句置于强调句型中来测试，首相应该用陈述句语序，还要出现it is that三个关键词，所以可以先排除A和B两个答案；另外结合句子中的具体语境可知需要句子prevent so many people from taking part in the program的主语,至此可知最佳答案为C.译文：当我们试着弄明白究竟是什么不能让如此多的人参加节目时，好象有两种主要的原因。
