too……to和so……that的语法结构

Question

例如He's too young to join the army.这句中to join the army在这句中作什么了？
还有She is so young that she can't look after herself.这句中that后面算式引导从句吗？如果是那是什么从句？

Answer 1

to join the army.和that she can't look after herself 都是做状语.这二个句型可以互换:He's too young to join the army=He's so young that he can't join the army

Answer 2

too.....to表示：“太......而不能”，固定搭配。
so......that表示：“如此.....以至于”引导结果状语从句。
1.他太年轻了不能加入军队。
2.她是如此的年轻，以至于不能照顾自己。

Answer 3

结果状语从句