The woman who is working in the office is my friend.换成that也可How grand buildings they are.这是错的改成：What grand buildings they are.how+adj+主语+谓语!how adj+a\an名词+主语+谓语!...都给我说说为什么，还有第一个问中的练习册答案是这样写的，强调用了who，为什么定语从句指人没特殊情况用who和that一样，这个句子都可以 只用who不用that 1）如果先行词是those,they,all,persons,people,he,anyone,one时用who不用that。 2）当先行词指人并含有较长的后置定语从句或在被分割的定语从句中时你说的这个句子不是特殊情况 How grand buildings they are.这是错的改成：What grand buildings they are. how+adj+主语+谓语！how adj+a\an+名词+主语+谓语！