Cal. Civ. Proc. Code § 2030.240

(a) If only a part of an interrogatory is objectionable, the remainder of the interrogatory shall be answered.

(b) If an objection is made to an interrogatory or to a part of an interrogatory, the specific ground for the objection shall be set forth clearly in the response. If an objection is based on a claim of privilege, the particular privilege invoked shall be clearly stated. If an objection is based on a claim that the information sought is protected work product under Chapter 4 (commencing with Section 2018.010), that claim shall be expressly asserted.