Cal. Civ. Proc. Code § 2033.230

(a) If only a part of a request for admission is objectionable, the remainder of the request shall be answered.

(b) If an objection is made to a request or to a part of a request, 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 matter as to which an admission is requested is protected work product under Chapter 4 (commencing with Section 2018.010), that claim shall be expressly asserted.