逗号+ but ... 后边往往跟着另外一个完整的句子。这是我从新概念2、3上的文章找到的所有句子的特点。例子很多。

没有逗号，直接跟but，往往后面是省略跟前面句子中相同的部分。下面是例子。

He started to complain about this wicked world but was interrupted by a knock at the door.  省略主语。
The explanation was simple but very unusual. 省略主语和was
The party then searched the whole cave thoroughly but did not find anything 省略主语
It was very different from modern car races but no less exciting. 省略主语和be动词。

所以你提到的句子里 逗号+but的用法，没有在新概念看到过类似的用法。
也可能每个人用标点、单词的习惯不同。如果按照新概念的用法，
She was a woman of about thirty but looked much older.
but前面没有逗号。

【 在 TexasPotato 的大作中提到: 】
: She was a woman of about thirty, but looking much older.
: She was a woman of about thirty, but looked much older.
: 哪个正确？
: ...................
--
FROM 111.193.228.*