Restrictive clauses are adjective clauses (They modify or gives further detail to nouns) that, unlike nonrestrictive clauses, are not separated or framed by commas and that are essential to the full meaning of the sentence: Without a restrictive clause, the meaning of a sentence would change, or the sentence would be incomplete and vague.
So, answer number 1, 2, 3 and 4 are all restrictive clauses for the following:
They modify nouns: Number 1 modifies "the girl", number 2 modifies "the dog", number three modifies "the muffins" and number 4 modifies "the smile"
They are essential to the full meaning of the sentence.