题目

When I try to find _____ that prevents so many people taking part in the program, it seems to me that there are two main causes.A. what it does B. what it isC. why it does D. why it is 答案：【答案】B【解析】考查强调句型。句意：当我努力想找出是什么阻止很多人参加这个节目时，我看似乎有两个原因。find后的宾语从句中包含一个强调句型，强调句型的特殊疑问句作宾语从句时要用陈述语气，结构为：特殊疑问词+ it is +that+其余部分，此处从句中缺少主语，故B项正确。 在等差数列中，若则=                A． B．           C． D．1