it was the way( )he walk ( )makes people laugh

C
楼主理解错误,第一个是定语从句,第二个才是强调句型.
1. 我把句子重新写过一遍：
It was the way (that he walk) that makes people laugh.
用括号括起来的就是定语从句,它是修饰the way的,而the way刚好又是强调句型所强调的主句的主语.
2. 此强调句写回原句如下：
The way (that he walks) makes people laugh.
带括号的同上,也是定语从句修饰主句主语the way.
然后强调上句的主语,就变成了：
It was the way (that he walk) that makes people laugh.
3. 相信写到这里,楼主应该已经明白了,不再赘述.

C
强调句
第一个空that是定语从句的引导词，第二个空that 是强调句的结构所需

第一个是定语从句连接词that 也可以是in which
第二个才是强调句的that