Question

dogs that have had special training to help people are service dogs. restrictive nonrestrictive no added clause

Explanation:

A restrictive clause provides essential information to identify the noun (here, "Dogs"). The clause "that have had special training to help people" is necessary to define which dogs are service dogs, so it's restrictive. Non - restrictive clauses are non - essential (set off by commas), and this clause isn't that. "No added clause" is incorrect as there is a clause.

Answer:

restrictive