Which clauses in these sentences are restrictive?
1.the girl with the golden hair is the one we are looking for.
2.the dog that ate my homework is called henry.
3.i’m saving the muffins that have cherries for my sister.
4.the smile that she gave them was beautiful
i don't get any of this

Restrictive clauses are relative to adjective clauses.

1. 'with the golden hair' would be describing the Girl, because her hair is Golden.
2. What describes the dog ? The dog 'that ate my homework'
3. What describes the muffins ? The muffins 'that have cherries'
4. What describes the smile ? The smile that she gave them was 'beautiful'

The adjectives phrases are in my apostrophes, hope you understand what restrictive clauses are now. :)

Because the vietnam war was fought in an especially brutal and untraditional way