这个语法结构帮我分析一下吧，谢谢？

Question

Taylor was supposed to be able to learn from the messages she received.为什么to be able要用be呢，为什么she received要放在最后呢？

Answer 1

因为able是形容词，to后面不能直接加形容词，需要加be组成不定式to be able ,表示能够……；she received 是massage的后置定语，其前省略了引导词that

Answer 2

固定用法：
be supposed to do sth 应该做某事
be able to do sth 能做某事
she received 是省略了引导词that/which 的定语从句修饰先行词messages.

Taylor was supposed to be able to learn from the messages she received.
泰勒应该能从她收到的信息中吸取教训。

追问

可是为什么要用be呢，为什么不用is wap呢

哈哈，明白了，谢谢🙏

追答

to 后跟动词原形
is,was 的原形是 be