Code of Civil Procedure CCP § 2032.230

(a) The plaintiff to whom a demand for a physical examination under this article is directed shall respond to the demand by a written statement that the examinee will comply with the demand as stated, will comply with the demand as specifically modified by the plaintiff, or will refuse, for reasons specified in the response, to submit to the demanded physical examination.

(b) Within 20 days after service of the demand the plaintiff to whom the demand is directed shall serve the original of the response to it on the defendant making the demand, and a copy of the response on all other parties who have appeared in the action.  On motion of the defendant making the demand, the court may shorten the time for response.  On motion of the plaintiff to whom the demand is directed, the court may extend the time for response.