Final answer:
The adjective clause 'who is a kind man' modifies the noun 'manager' in the sentence provided, clarifying that the manager is a kind person.
Step-by-step explanation:
The entire adjective clause in the sentence 'The manager, who is a kind man, helped us.' is 'who is a kind man' and it modifies the noun 'manager'. This adjective clause provides additional information about the manager, indicating that they are a kind person. The adjective clause begins with the relative pronoun 'who', which relates back to the noun it is modifying, in this case, 'manager'. Therefore, the correct answer to the student's question is 'who is a kind man; modifies "manager"', which corresponds to option b.