California Code of Civil Procedure
Code of Civil Procedure section 2030.210
(a) The party to whom interrogatories have been propounded shall respond in writing under oath separately to each interrogatory by any of the following:
(1) An answer containing the information sought to be discovered.
(2) An exercise of the party's option to produce writings.
(3) An objection to the particular interrogatory.
(b) In the first paragraph of the response immediately below the title of the case, there shall appear the identity of the responding party, the set number, and the identity of the propounding party.
(c) Each answer, exercise of option, or objection in the response shall bear the same identifying number or letter and be in the same sequence as the corresponding interrogatory, but the text of that interrogatory need not be repeated.