定语从句与介词的宾语从句：

答案：B 解释：1。 of which放在the walls的前面也可以,放在the walls的后面也可以。定语从句为：the walls of which are painted light green= the walls of the (newly built) cafe are painted light green即关系代词which代指先行词the (newly built) cafe,并在定语从句中充当介词of的宾语。而定语从句的主语是the walls,of which为介词短语做后置定语修饰该主语。所以该定语从句并不是楼主所说的那样没有主语。当然该定语从句也可以使用whose来引导,但是定语从句须变成：whose walls are painted light green= (the cafe's) walls are painted light green2。 关键是对句子成分结构的判断。主句为：The newly built cafe is really a peaceful place for us, especially after hard work。所以逗号中间的部分只能做非限制性定语从句了。如果用what,则what只能引导名词性从句（即所谓的主语从句,宾语从句或表语从句等）,而不能引导定语从句或状语从句。但是整个主句（The newly built cafe is really a peaceful place for us, especially after hard work。。）并不缺少什么主语,宾语或表语,所以A是错误的。