but not用法

cruel to them
but not（be）省略了动词，使文章变得简洁，所以cruel to them 应与kind to animals 保持一致，即形容词对形容词，to对to

1、but... not... 转折+否定句
She's well singing, but she didn't have ever been performing on any stage.
2、not... but... 不是…而是…
He's not a student but a teacher in the school.
3、not only... but also... 不仅…而且…（经典）
Not only adults but also youngsters may as reckon it's impossibly correct.
4、亦可用never, harldly等表示否定的词代替 not，上述句子亦同
I never feel a bit embarrassing for anything bad they did but you did.

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