Texas Civil Practice and Remedies Code - CIV PRAC & REM § 140A.058. Interrogatories

(a) Each interrogatory in any civil investigative demand duly served must be answered separately and fully in writing, unless it is objected to, in which case the basis for the objection shall be set forth in lieu of an answer.  The person shall indicate in writing which, if any, of the answers contain trade secrets or confidential information.

(b) Answers to interrogatories must be submitted under a sworn certificate in the form the related demand designates by a natural person having knowledge of the facts and circumstances relating to the preparation of the answers to the effect that all of the requested information in the possession, custody, control, or knowledge of the person to whom the demand is directed has been set forth fully and accurately.