【一】The other day, my brother drove his car down the street at ______ I thought was a dangerous speed.

A. as B. which C. what D. that

解答如下：以上C为正确答案，at what I thought was a dangerous speed.为介词宾语从句， 即介词“at”+what引导的宾语从句，what 引导的宾语从句属于嵌入式宾语从句《备注：有的人把I thought当作插入语理解》，what作宾语从句的主语成分。

如果选择B/D，则按照定语从句理解，at which作状语，与句子意思发生逻辑错误，that引导定语从句，不能放在介词后作宾语。

【二】关于插入语解答

【A】What do you think has happened to her？

解答：以上“do you think”为插入语用来表达说话人的观点，what在特殊疑问句充当“主语”成分。后面结构用陈述语序。

备注：what为宾语从句主语，has happened为宾语从句谓语动词，to her为宾语从句对象状语。do you think为插入语。

为了让你有一个更加清楚理解，我给你演绎一下。

I think a car accident has happened to her.

如果对红色字体提问，也就是宾语从句主语提问，就是下面第1个正确句子

【1】What do you think has happened to her?【正确】

【2】Do you think what has happened to her?【错误】

【B】What do you think of your new department？

 解答如下：以上“do you think”不是插入语结构，而是一个“特殊疑问句+一般疑问句结构”即“What do you think of +名词(sth)=你认为某物怎么样” what为谓语动词think 的间接宾语，do为疑问助动词（操作词），you为主语，of your new department为直接宾语，即结构为：think sth of sth/sb 对某人/某物评价怎样

The Director thought a good deal of his work.主任对他的工作评价很高。

 They think much of psychiatrists.他们对精神科医生评价很高。

备注：What do you think of +名词(sth)？=How do you like +名词(sth)?

【C】What do you think that Sally will do中，

解答如下：

以上“that”是多余的，应该去掉：正确应该是What do you think Sally will do? “do you think”可以按照“插入语理解”what在句子作will do的宾语成分。

备注：what为宾语从句宾语成分，will do为宾语从句谓语动词，Sally为宾语从句主语成分，do you think为插入语。

【D】How much do you think he earns every day中

解答如下：

以上“do you think”为插入语，how much在句子作谓语动词“earns”的宾语成分。

备注：how much为宾语从句宾语，earns为宾语从句谓语动词，he为宾语从句主语。do you think为插入语。

为了让你有一个更加清楚理解，我给你演绎一下。

I think he earns three hundred USD every day.

如果对红色字体提问，也就是宾语从句宾语提问，就是下面的第1个正确句子

【1】How much do you think he earns every day?【正确】

【2】Do you think how much he earns every day?【错误】

 【E】What do you think that happened to him，这句话是不是病句？

解答如下：

以上“that”为多余成分。正确应该是“What do you think happened to him?”

备注：含有插入句子句子结构为

【1】特殊疑问词+do you think +主语+谓语动词

备注：在1句型中 疑问句代词在句中不作主语，即不作宾语从句主语，而是作句子其它成分。

【2】特殊疑问词+do you think+谓语动词

备注：在2 句型中 疑问句代词在句中作主语，即作宾语从句主语。

为了让你有一个更加清楚理解，我给你演绎一下。

I think a car accident happened to him.

如果对红色字体提问，也就是宾语从句主语提问，就是下面第1个正确句子

【1】What do you think happened to him?【正确】

【2】Do you think what happened to him?【错误】